chore(deps): update Go dependencies

* add new metadata functions to pdf engine interface

* add exiftool module with relevant test cases

* use exiftool to overwrite metadata in libreoffice

* use exiftool to overwrite metadata in chromium

* fix linter issues

* fix more linter issues

* more test cases for better coverage

* remove utils

* minor changes

* remove metadata from pdfoptions

* correct indentation

* read/write metadata one file at a time.

.golangci.yml

@@ -10,20 +10,44 @@ linters-settings:
 linters:
   disable-all: true
   enable:
+    - asasalint
+    - asciicheck
+    - bidichk
     - bodyclose
+    - decorder
+    - dogsled
+    - dupl
+    - dupword
+    - durationcheck
     - errcheck
+    - errname
+    - exhaustive
+    - exportloopref
     - gci
+    - gofmt
+    - goimports
     - gofumpt
     - gosec
     - gosimple
     - govet
     - ineffassign
+    - importas
     - misspell
     - prealloc
+    - promlinter
+    - sloglint
+    - sqlclosecheck
     - staticcheck
+    - tenv
+    - testableexamples
+    - testifylint
+    - tparallel
     - typecheck
     - unconvert
     - unused
+    - wastedassign
+    - whitespace
+    - zerologlint
 
 run:
   timeout: 5m
@@ -31,6 +55,5 @@ run:
   tests: false
 
 output:
-  format: 'colored-line-number'
   print-issued-lines: true
   print-linter-name: true

build/Dockerfile

@@ -164,19 +164,20 @@ RUN \
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 RUN \
-    # Install PDFtk & QPDF (PDF engines).
+    # Install PDFtk, QPDF & ExifTool (PDF engines).
     # See https://github.com/gotenberg/gotenberg/pull/273.
     curl -o /usr/bin/pdftk-all.jar "https://gitlab.com/api/v4/projects/5024297/packages/generic/pdftk-java/$PDFTK_VERSION/pdftk-all.jar" &&\
     chmod a+x /usr/bin/pdftk-all.jar &&\
     echo '#!/bin/bash\n\nexec java -jar /usr/bin/pdftk-all.jar "$@"' > /usr/bin/pdftk && \
     chmod +x /usr/bin/pdftk &&\
     apt-get update -qq &&\
-    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends qpdf &&\
+    DEBIAN_FRONTEND=noninteractive apt-get install -y -qq --no-install-recommends qpdf exiftool &&\
     # See https://github.com/nextcloud/docker/issues/380.
     mkdir -p /usr/share/man/man1 &&\
     # Verify installations.
     pdftk --version &&\
     qpdf --version &&\
+    exiftool --version &&\
     # Cleanup.
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
@@ -195,6 +196,7 @@ ENV LIBREOFFICE_BIN_PATH /usr/lib/libreoffice/program/soffice.bin
 ENV UNOCONVERTER_BIN_PATH /usr/bin/unoconverter
 ENV PDFTK_BIN_PATH /usr/bin/pdftk
 ENV QPDF_BIN_PATH /usr/bin/qpdf
+ENV EXIFTOOL_BIN_PATH /usr/bin/exiftool
 
 USER gotenberg
 WORKDIR /home/gotenberg

go.mod

@@ -1,10 +1,11 @@
 module github.com/gotenberg/gotenberg/v8
 
-go 1.22
+go 1.21
 
 require (
 	github.com/alexliesenfeld/health v0.8.0
 	github.com/andybalholm/brotli v1.1.0 // indirect
+	github.com/barasher/go-exiftool v1.10.0
 	github.com/chromedp/cdproto v0.0.0-20240312231614-1e5096e63154
 	github.com/chromedp/chromedp v0.9.5
 	github.com/golang/snappy v0.0.4 // indirect
@@ -56,7 +57,7 @@ require (
 	github.com/mattn/go-runewidth v0.0.15 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/prometheus/client_model v0.6.0 // indirect
-	github.com/prometheus/common v0.50.0 // indirect
+	github.com/prometheus/common v0.51.0 // indirect
 	github.com/prometheus/procfs v0.13.0 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/valyala/bytebufferpool v1.0.0 // indirect

go.sum

@@ -5,6 +5,8 @@ github.com/andybalholm/brotli v1.1.0 h1:eLKJA0d02Lf0mVpIDgYnqXcUn0GqVmEFny3VuID1
 github.com/andybalholm/brotli v1.1.0/go.mod h1:sms7XGricyQI9K10gOSf56VKKWS4oLer58Q+mhRPtnY=
 github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuPk=
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
+github.com/barasher/go-exiftool v1.10.0 h1:f5JY5jc42M7tzR6tbL9508S2IXdIcG9QyieEXNMpIhs=
+github.com/barasher/go-exiftool v1.10.0/go.mod h1:F9s/a3uHSM8YniVfwF+sbQUtP8Gmh9nyzigNF+8vsWo=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
@@ -16,6 +18,7 @@ github.com/chromedp/chromedp v0.9.5 h1:viASzruPJOiThk7c5bueOUY91jGLJVximoEMGoH93
 github.com/chromedp/chromedp v0.9.5/go.mod h1:D4I2qONslauw/C7INoCir1BJkSwBYMyZgx8X276z3+Y=
 github.com/chromedp/sysutil v1.0.0 h1:+ZxhTpfpZlmchB58ih/LBHX52ky7w2VhQVKQMucy3Ic=
 github.com/chromedp/sysutil v1.0.0/go.mod h1:kgWmDdq8fTzXYcKIBqIYvRRTnYb9aNS9moAV0xufSww=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dlclark/regexp2 v1.11.0 h1:G/nrcoOa7ZXlpoa/91N3X7mM3r8eIlMBBJZvsz/mxKI=
@@ -100,8 +103,8 @@ github.com/prometheus/client_golang v1.19.0 h1:ygXvpU1AoN1MhdzckN+PyD9QJOSD4x7km
 github.com/prometheus/client_golang v1.19.0/go.mod h1:ZRM9uEAypZakd+q/x7+gmsvXdURP+DABIEIjnmDdp+k=
 github.com/prometheus/client_model v0.6.0 h1:k1v3CzpSRUTrKMppY35TLwPvxHqBu0bYgxZzqGIgaos=
 github.com/prometheus/client_model v0.6.0/go.mod h1:NTQHnmxFpouOD0DpvP4XujX3CdOAGQPoaGhyTchlyt8=
-github.com/prometheus/common v0.50.0 h1:YSZE6aa9+luNa2da6/Tik0q0A5AbR+U003TItK57CPQ=
-github.com/prometheus/common v0.50.0/go.mod h1:wHFBCEVWVmHMUpg7pYcOm2QUR/ocQdYSJVQJKnHc3xQ=
+github.com/prometheus/common v0.51.0 h1:vT5R9NAlW4V6k8Wruk7ikrHaHRsrPbduM/cKTOdQM/k=
+github.com/prometheus/common v0.51.0/go.mod h1:wHFBCEVWVmHMUpg7pYcOm2QUR/ocQdYSJVQJKnHc3xQ=
 github.com/prometheus/procfs v0.13.0 h1:GqzLlQyfsPbaEHaQkO7tbDlriv/4o5Hudv6OXHGKX7o=
 github.com/prometheus/procfs v0.13.0/go.mod h1:cd4PFCR54QLnGKPaKGA6l+cfuNXtht43ZKY6tow0Y1g=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
@@ -113,9 +116,11 @@ github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.5.0 h1:1zr/of2m5FGMsad5YfcqgdqdWrIhu+EBEJRhR1U7z/c=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/ulikunitz/xz v0.5.8/go.mod h1:nbz6k7qbPmH4IRqmfOplQw/tblSgqTqBwxkY0oWt/14=

pkg/gotenberg/mocks.go

@@ -35,8 +35,10 @@ func (mod *ValidatorMock) Validate() error {
 
 // PdfEngineMock is a mock for the [PdfEngine] interface.
 type PdfEngineMock struct {
-	MergeMock   func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error
-	ConvertMock func(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error
+	MergeMock         func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error
+	ConvertMock       func(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error
+	ReadMetadataMock  func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error)
+	WriteMetadataMock func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error
 }
 
 func (engine *PdfEngineMock) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
@@ -47,6 +49,14 @@ func (engine *PdfEngineMock) Convert(ctx context.Context, logger *zap.Logger, fo
 	return engine.ConvertMock(ctx, logger, formats, inputPath, outputPath)
 }
 
+func (engine *PdfEngineMock) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	return engine.ReadMetadataMock(ctx, logger, inputPath)
+}
+
+func (engine *PdfEngineMock) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	return engine.WriteMetadataMock(ctx, logger, metadata, inputPath)
+}
+
 // PdfEngineProviderMock is a mock for the [PdfEngineProvider] interface.
 type PdfEngineProviderMock struct {
 	PdfEngineMock func() (PdfEngine, error)

pkg/gotenberg/mocks_test.go

@@ -55,6 +55,12 @@ func TestPDFEngineMock(t *testing.T) {
 		ConvertMock: func(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error {
 			return nil
 		},
+		ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+			return nil, nil
+		},
+		WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+			return nil
+		},
 	}
 
 	err := mock.Merge(context.Background(), zap.NewNop(), nil, "")
@@ -66,6 +72,16 @@ func TestPDFEngineMock(t *testing.T) {
 	if err != nil {
 		t.Errorf("expected no error from PdfEngineMock.Convert, but got: %v", err)
 	}
+
+	_, err = mock.ReadMetadata(context.Background(), zap.NewNop(), "")
+	if err != nil {
+		t.Errorf("expected no error from PdfEngineMock.ReadMetadata, but got: %v", err)
+	}
+
+	err = mock.WriteMetadata(context.Background(), zap.NewNop(), map[string]interface{}{}, "")
+	if err != nil {
+		t.Errorf("expected no error from PdfEngineMock.WriteMetadata but got: %v", err)
+	}
 }
 
 func TestPDFEngineProviderMock(t *testing.T) {

pkg/gotenberg/pdfengine.go

@@ -15,6 +15,10 @@ var (
 	// ErrPdfFormatNotSupported is returned when the Convert method of the
 	// PdfEngine interface does not support a requested PDF format conversion.
 	ErrPdfFormatNotSupported = errors.New("PDF format not supported")
+
+	// ErrPdfEngineMetadataValueNotSupported is returned when a metadata value
+	// is not supported.
+	ErrPdfEngineMetadataValueNotSupported = errors.New("metadata value not supported")
 )
 
 const (
@@ -64,6 +68,12 @@ type PdfEngine interface {
 	// Convert transforms a given PDF to the specified formats defined in
 	// PdfFormats. If no format, it does nothing.
 	Convert(ctx context.Context, logger *zap.Logger, formats PdfFormats, inputPath, outputPath string) error
+
+	// ReadMetadata extracts the metadata of a given PDF file.
+	ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error)
+
+	// WriteMetadata writes the metadata into a given PDF file.
+	WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error
 }
 
 // PdfEngineProvider offers an interface to instantiate a [PdfEngine].

pkg/gotenberg/sort.go

@@ -9,7 +9,7 @@ import (
 // AlphanumericSort implements sort.Interface and helps to sort strings
 // alphanumerically.
 //
-// See https://github.com/gotenberg/gotenberg/issues/805.
+// See: https://github.com/gotenberg/gotenberg/issues/805.
 type AlphanumericSort []string
 
 func (s AlphanumericSort) Len() int {

pkg/modules/api/api.go

@@ -402,7 +402,7 @@ func (a *Api) Start() error {
 			a.srv.Pre(externalMiddleware.Handler)
 		case MultipartStack:
 			externalMultipartMiddlewares = append(externalMultipartMiddlewares, externalMiddleware)
-		default:
+		case DefaultStack:
 			a.srv.Use(externalMiddleware.Handler)
 		}
 	}

pkg/modules/api/context.go

@@ -93,7 +93,6 @@ func newContext(echoCtx echo.Context, logger *zap.Logger, fs *gotenberg.FileSyst
 
 	form, err := echoCtx.MultipartForm()
 	if err != nil {
-
 		if errors.Is(err, http.ErrNotMultipart) {
 			return nil, cancel, WrapError(
 				fmt.Errorf("get multipart form: %w", err),

pkg/modules/api/formdata.go

@@ -2,6 +2,7 @@ package api
 
 import (
 	"fmt"
+	"math"
 	"net/http"
 	"os"
 	"path/filepath"
@@ -145,6 +146,91 @@ func (form *FormData) MandatoryDuration(key string, target *time.Duration) *Form
 	return form.mustMandatoryField(key, target)
 }
 
+// Inches binds a form field to a float64 variable. It populates an error
+// if the value cannot be computed back to inches.
+//
+//	var foo float64
+//
+//	ctx.FormData().Inches("foo", &foo, 2.0)
+func (form *FormData) Inches(key string, target *float64, defaultValue float64) *FormData {
+	form.inches(key, target)
+	if *target == -math.MaxFloat64 {
+		*target = defaultValue
+	}
+	return form
+}
+
+// MandatoryInches binds a form field to a float64 variable. It populates
+// an error if the value cannot be computed back to inches, is empty, or the
+// "key" does not exist.
+//
+//	var foo float64
+//
+//	ctx.FormData().MandatoryInches("foo", &foo)
+func (form *FormData) MandatoryInches(key string, target *float64) *FormData {
+	val, ok := form.values[key]
+	if !ok || val[0] == "" {
+		form.append(
+			fmt.Errorf("form field '%s' is required", key),
+		)
+		return form
+	}
+	return form.inches(key, target)
+}
+
+// inches tries to compute a string value to inches.
+func (form *FormData) inches(key string, target *float64) *FormData {
+	var value string
+	form.mustValue(key, &value, "")
+
+	if value == "" {
+		*target = -math.MaxFloat64
+		return form
+	}
+
+	for _, unit := range []string{"pt", "px", "in", "mm", "cm", "pc"} {
+		if !strings.HasSuffix(value, unit) {
+			continue
+		}
+
+		val, err := strconv.ParseFloat(strings.TrimSuffix(value, unit), 64)
+		if err != nil {
+			form.append(
+				fmt.Errorf("form field '%s' is invalid (got '%s', resulting to %w)", key, value, err),
+			)
+			return form
+		}
+
+		switch unit {
+		case "pt":
+			*target = val * (1.0 / 72.0)
+		case "px":
+			*target = val * (1.0 / 96.0)
+		case "in":
+			*target = val
+		case "mm":
+			*target = val * (1.0 / 25.4)
+		case "cm":
+			*target = val * (1.0 / 2.54)
+		case "pc":
+			*target = val * (1.0 / 6.0)
+		}
+
+		return form
+	}
+
+	val, err := strconv.ParseFloat(value, 64)
+	if err != nil {
+		form.append(
+			fmt.Errorf("form field '%s' is invalid (got '%s', resulting to %w)", key, value, err),
+		)
+		return form
+	}
+
+	*target = val
+	return form
+}
+
 // Custom helps to define a custom binding function for a form field.
 //
 //	var foo map[string]string

pkg/modules/api/formdata_test.go

@@ -3,6 +3,7 @@ package api
 import (
 	"encoding/json"
 	"errors"
+	"fmt"
 	"reflect"
 	"testing"
 	"time"
@@ -768,6 +769,333 @@ func TestFormData_MandatoryDuration(t *testing.T) {
 	}
 }
 
+func TestFormData_Inches(t *testing.T) {
+	for _, tc := range []struct {
+		scenario     string
+		form         *FormData
+		defaultValue float64
+		expect       float64
+		expectError  bool
+	}{
+		{
+			scenario:     "key does not exist, fallback to default zero value",
+			form:         &FormData{},
+			defaultValue: 0.0,
+			expect:       0.0,
+			expectError:  false,
+		},
+		{
+			scenario:     "key does not exist, fallback to default value",
+			form:         &FormData{},
+			defaultValue: 2.5,
+			expect:       2.5,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist, but empty value, fallback to default value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       0.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist, value has a unit, but the rest is not float64 compatible",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"foomm",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       0.0,
+			expectError:  true,
+		},
+		{
+			scenario: "key does exist, but value has no unit and is invalid",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"foo",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       0.0,
+			expectError:  true,
+		},
+		{
+			scenario: "key does exist with a pt value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"72pt",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with a px value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"96px",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with an in value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"1in",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with a mm value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"25.4mm",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with a cm value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"2.54cm",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with a pc value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"6pc",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       1.0,
+			expectError:  false,
+		},
+		{
+			scenario: "key does exist with no unit in the value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"100",
+					},
+				},
+			},
+			defaultValue: 0.0,
+			expect:       100,
+			expectError:  false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			var actual float64
+
+			tc.form.Inches("foo", &actual, tc.defaultValue)
+
+			if fmt.Sprintf("%.1f", actual) != fmt.Sprintf("%.1f", tc.expect) {
+				t.Errorf("expected %.1f but got %.1f", tc.expect, actual)
+			}
+
+			if tc.expectError && tc.form.errors == nil {
+				t.Fatal("expected error but got none", tc.form.errors)
+			}
+
+			if !tc.expectError && tc.form.errors != nil {
+				t.Fatalf("expected no error but got: %v", tc.form.errors)
+			}
+		})
+	}
+}
+
+func TestFormData_MandatoryInches(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		form        *FormData
+		expect      float64
+		expectError bool
+	}{
+		{
+			scenario:    "missing mandatory key",
+			form:        &FormData{},
+			expect:      0.0,
+			expectError: true,
+		},
+		{
+			scenario: "mandatory value is empty",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"",
+					},
+				},
+			},
+			expect:      0.0,
+			expectError: true,
+		},
+		{
+			scenario: "mandatory value has a unit, but the rest is not float64 compatible",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"foomm",
+					},
+				},
+			},
+			expect:      0.0,
+			expectError: true,
+		},
+		{
+			scenario: "mandatory value has no unit and is invalid",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"foo",
+					},
+				},
+			},
+			expect:      0.0,
+			expectError: true,
+		},
+		{
+			scenario: "a pt mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"72pt",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "a px mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"96px",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "an in mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"1in",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "a mm mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"25.4mm",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "a cm mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"2.54cm",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "a pc mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"6pc",
+					},
+				},
+			},
+			expect:      1.0,
+			expectError: false,
+		},
+		{
+			scenario: "no unit in the mandatory value",
+			form: &FormData{
+				values: map[string][]string{
+					"foo": {
+						"100",
+					},
+				},
+			},
+			expect:      100,
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			var actual float64
+
+			tc.form.MandatoryInches("foo", &actual)
+
+			if fmt.Sprintf("%.1f", actual) != fmt.Sprintf("%.1f", tc.expect) {
+				t.Errorf("expected %.1f but got %.1f", tc.expect, actual)
+			}
+
+			if tc.expectError && tc.form.errors == nil {
+				t.Fatal("expected error but got none", tc.form.errors)
+			}
+
+			if !tc.expectError && tc.form.errors != nil {
+				t.Fatalf("expected no error but got: %v", tc.form.errors)
+			}
+		})
+	}
+}
+
 func TestFormData_Custom(t *testing.T) {
 	for _, tc := range []struct {
 		scenario     string

pkg/modules/api/middlewares.go

@@ -15,9 +15,15 @@ import (
 	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
 )
 
-// ErrAsyncProcess happens when a handler or middleware handles a request in an
-// asynchronous fashion.
-var ErrAsyncProcess = errors.New("async process")
+var (
+	// ErrAsyncProcess happens when a handler or middleware handles a request
+	// in an asynchronous fashion.
+	ErrAsyncProcess = errors.New("async process")
+
+	// ErrNoOutputFile happens when a handler or middleware handles a request
+	// without sending any output file.
+	ErrNoOutputFile = errors.New("no output file")
+)
 
 // ParseError parses an error and returns the corresponding HTTP status and
 // HTTP message.
@@ -44,6 +50,10 @@ func ParseError(err error) (int, string) {
 		return http.StatusBadRequest, "At least one PDF engine cannot process the requested PDF format, while others may have failed to convert due to different issues"
 	}
 
+	if errors.Is(err, gotenberg.ErrPdfEngineMetadataValueNotSupported) {
+		return http.StatusBadRequest, "At least one PDF engine cannot process the requested metadata, while others may have failed to convert due to different issues"
+	}
+
 	var httpErr HttpError
 	if errors.As(err, &httpErr) {
 		return httpErr.HttpError()
@@ -242,6 +252,13 @@ func contextMiddleware(fs *gotenberg.FileSystem, timeout time.Duration) echo.Mid
 
 			defer cancel()
 
+			if errors.Is(err, ErrNoOutputFile) {
+				// A middleware/handler tells us that it's handling the process
+				// in an asynchronous fashion. Therefore, we must not cancel
+				// the context nor send an output file.
+				return nil
+			}
+
 			if err != nil {
 				return err
 			}

pkg/modules/api/middlewares_test.go

@@ -43,6 +43,11 @@ func TestParseError(t *testing.T) {
 			expectStatus:  http.StatusBadRequest,
 			expectMessage: "At least one PDF engine cannot process the requested PDF format, while others may have failed to convert due to different issues",
 		},
+		{
+			err:           gotenberg.ErrPdfEngineMetadataValueNotSupported,
+			expectStatus:  http.StatusBadRequest,
+			expectMessage: "At least one PDF engine cannot process the requested metadata, while others may have failed to convert due to different issues",
+		},
 		{
 			err: WrapError(
 				errors.New("foo"),
@@ -330,6 +335,15 @@ func TestContextMiddleware(t *testing.T) {
 			}(),
 			expectStatus: http.StatusNoContent,
 		},
+		{
+			request: buildMultipartFormDataRequest(),
+			next: func() echo.HandlerFunc {
+				return func(c echo.Context) error {
+					return ErrNoOutputFile
+				}
+			}(),
+			expectStatus: http.StatusOK,
+		},
 		{
 			request: buildMultipartFormDataRequest(),
 			next: func() echo.HandlerFunc {

pkg/modules/chromium/routes.go

@@ -78,7 +78,7 @@ func FormDataChromiumOptions(ctx *api.Context) (*api.FormData, Options) {
 			}
 
 			if value != "screen" && value != "print" {
-				return fmt.Errorf("wrong value, expected either 'screen', 'print' or empty")
+				return errors.New("wrong value, expected either 'screen', 'print' or empty")
 			}
 
 			emulatedMediaType = value
@@ -122,12 +122,12 @@ func FormDataChromiumPdfOptions(ctx *api.Context) (*api.FormData, PdfOptions) {
 		Bool("printBackground", &printBackground, defaultPdfOptions.PrintBackground).
 		Float64("scale", &scale, defaultPdfOptions.Scale).
 		Bool("singlePage", &singlePage, defaultPdfOptions.SinglePage).
-		Float64("paperWidth", &paperWidth, defaultPdfOptions.PaperWidth).
-		Float64("paperHeight", &paperHeight, defaultPdfOptions.PaperHeight).
-		Float64("marginTop", &marginTop, defaultPdfOptions.MarginTop).
-		Float64("marginBottom", &marginBottom, defaultPdfOptions.MarginBottom).
-		Float64("marginLeft", &marginLeft, defaultPdfOptions.MarginLeft).
-		Float64("marginRight", &marginRight, defaultPdfOptions.MarginRight).
+		Inches("paperWidth", &paperWidth, defaultPdfOptions.PaperWidth).
+		Inches("paperHeight", &paperHeight, defaultPdfOptions.PaperHeight).
+		Inches("marginTop", &marginTop, defaultPdfOptions.MarginTop).
+		Inches("marginBottom", &marginBottom, defaultPdfOptions.MarginBottom).
+		Inches("marginLeft", &marginLeft, defaultPdfOptions.MarginLeft).
+		Inches("marginRight", &marginRight, defaultPdfOptions.MarginRight).
 		String("nativePageRanges", &pageRanges, defaultPdfOptions.PageRanges).
 		Content("header.html", &headerTemplate, defaultPdfOptions.HeaderTemplate).
 		Content("footer.html", &footerTemplate, defaultPdfOptions.FooterTemplate).
@@ -233,6 +233,21 @@ func FormDataChromiumPdfFormats(form *api.FormData) gotenberg.PdfFormats {
 	}
 }
 
+// FormDataPdfMetadata creates metadata object from the form data.
+func FormDataPdfMetadata(form *api.FormData) map[string]interface{} {
+	var metadata map[string]interface{}
+	form.Custom("metadata", func(value string) error {
+		if len(value) > 0 {
+			err := json.Unmarshal([]byte(value), &metadata)
+			if err != nil {
+				return fmt.Errorf("unmarshal metadata: %w", err)
+			}
+		}
+		return nil
+	})
+	return metadata
+}
+
 // convertUrlRoute returns an [api.Route] which can convert a URL to PDF.
 func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 	return api.Route{
@@ -243,6 +258,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
 			pdfFormats := FormDataChromiumPdfFormats(form)
+			metadata := FormDataPdfMetadata(form)
 
 			var url string
 			err := form.
@@ -252,7 +268,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("validate form data: %w", err)
 			}
 
-			err = convertUrl(ctx, chromium, engine, url, pdfFormats, options)
+			err = convertUrl(ctx, chromium, engine, url, options, pdfFormats, metadata)
 			if err != nil {
 				return fmt.Errorf("convert URL to PDF: %w", err)
 			}
@@ -302,6 +318,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
 			pdfFormats := FormDataChromiumPdfFormats(form)
+			metadata := FormDataPdfMetadata(form)
 
 			var inputPath string
 			err := form.
@@ -312,7 +329,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			}
 
 			url := fmt.Sprintf("file://%s", inputPath)
-			err = convertUrl(ctx, chromium, engine, url, pdfFormats, options)
+			err = convertUrl(ctx, chromium, engine, url, options, pdfFormats, metadata)
 			if err != nil {
 				return fmt.Errorf("convert HTML to PDF: %w", err)
 			}
@@ -363,6 +380,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			ctx := c.Get("context").(*api.Context)
 			form, options := FormDataChromiumPdfOptions(ctx)
 			pdfFormats := FormDataChromiumPdfFormats(form)
+			metadata := FormDataPdfMetadata(form)
 
 			var (
 				inputPath     string
@@ -382,7 +400,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("transform markdown file(s) to HTML: %w", err)
 			}
 
-			err = convertUrl(ctx, chromium, engine, url, pdfFormats, options)
+			err = convertUrl(ctx, chromium, engine, url, options, pdfFormats, metadata)
 			if err != nil {
 				return fmt.Errorf("convert markdown to PDF: %w", err)
 			}
@@ -506,7 +524,7 @@ func markdownToHtml(ctx *api.Context, inputPath string, markdownPaths []string)
 	return fmt.Sprintf("file://%s", inputPath), nil
 }
 
-func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url string, pdfFormats gotenberg.PdfFormats, options PdfOptions) error {
+func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url string, options PdfOptions, pdfFormats gotenberg.PdfFormats, metadata map[string]interface{}) error {
 	outputPath := ctx.GeneratePath(".pdf")
 
 	err := chromium.Pdf(ctx, ctx.Log(), url, outputPath, options)
@@ -562,6 +580,14 @@ func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url
 		outputPath = convertOutputPath
 	}
 
+	// Writes and potentially overrides metadata entries, if any.
+	if len(metadata) > 0 {
+		err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
+		if err != nil {
+			return fmt.Errorf("write metadata: %w", err)
+		}
+	}
+
 	err = ctx.AddOutputPaths(outputPath)
 	if err != nil {
 		return fmt.Errorf("add output path: %w", err)

pkg/modules/chromium/routes_test.go

@@ -399,6 +399,57 @@ func TestFormDataChromiumPdfFormats(t *testing.T) {
 	}
 }
 
+func TestFormDataPdfMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario         string
+		ctx              *api.ContextMock
+		expectedMetadata map[string]interface{}
+	}{
+		{
+			scenario:         "no metadata form field",
+			ctx:              &api.ContextMock{Context: new(api.Context)},
+			expectedMetadata: nil,
+		},
+		{
+			scenario: "invalid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"foo",
+					},
+				})
+				return ctx
+			}(),
+			expectedMetadata: nil,
+		},
+		{
+			scenario: "valid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"foo\":\"bar\"}",
+					},
+				})
+				return ctx
+			}(),
+			expectedMetadata: map[string]interface{}{
+				"foo": "bar",
+			},
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			tc.ctx.SetLogger(zap.NewNop())
+			actual := FormDataPdfMetadata(tc.ctx.Context.FormData())
+
+			if !reflect.DeepEqual(actual, tc.expectedMetadata) {
+				t.Fatalf("expected %+v but got: %+v", tc.expectedMetadata, actual)
+			}
+		})
+	}
+}
+
 func TestConvertUrlRoute(t *testing.T) {
 	for _, tc := range []struct {
 		scenario               string
@@ -1223,8 +1274,9 @@ func TestConvertUrl(t *testing.T) {
 		ctx                    *api.ContextMock
 		api                    Api
 		engine                 gotenberg.PdfEngine
-		pdfFormats             gotenberg.PdfFormats
 		options                PdfOptions
+		pdfFormats             gotenberg.PdfFormats
+		metadata               map[string]interface{}
 		expectError            bool
 		expectHttpError        bool
 		expectHttpStatus       int
@@ -1330,7 +1382,7 @@ func TestConvertUrl(t *testing.T) {
 			expectOutputPathsCount: 0,
 		},
 		{
-			scenario: "error from PDF engine",
+			scenario: "PDF engine convert error",
 			ctx:      &api.ContextMock{Context: new(api.Context)},
 			api: &ApiMock{PdfMock: func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
 				return nil
@@ -1338,14 +1390,14 @@ func TestConvertUrl(t *testing.T) {
 			engine: &gotenberg.PdfEngineMock{ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 				return errors.New("foo")
 			}},
-			pdfFormats:             gotenberg.PdfFormats{PdfA: "foo"},
 			options:                DefaultPdfOptions(),
+			pdfFormats:             gotenberg.PdfFormats{PdfA: "foo"},
 			expectError:            true,
 			expectHttpError:        false,
 			expectOutputPathsCount: 0,
 		},
 		{
-			scenario: "success with pdfa form field",
+			scenario: "success with PDF formats",
 			ctx:      &api.ContextMock{Context: new(api.Context)},
 			api: &ApiMock{PdfMock: func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
 				return nil
@@ -1353,12 +1405,29 @@ func TestConvertUrl(t *testing.T) {
 			engine: &gotenberg.PdfEngineMock{ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
 				return nil
 			}},
-			pdfFormats:             gotenberg.PdfFormats{PdfA: gotenberg.PdfA1b},
 			options:                DefaultPdfOptions(),
+			pdfFormats:             gotenberg.PdfFormats{PdfA: gotenberg.PdfA1b},
 			expectError:            false,
 			expectHttpError:        false,
 			expectOutputPathsCount: 1,
 		},
+		{
+			scenario: "PDF engine write metadata error",
+			ctx:      &api.ContextMock{Context: new(api.Context)},
+			api: &ApiMock{PdfMock: func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
+				return nil
+			}},
+			engine: &gotenberg.PdfEngineMock{WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+				return errors.New("foo")
+			}},
+			options: DefaultPdfOptions(),
+			metadata: map[string]interface{}{
+				"Creator":  "foo",
+				"Producer": "bar",
+			},
+			expectError:     true,
+			expectHttpError: false,
+		},
 		{
 			scenario: "cannot add output paths",
 			ctx: func() *api.ContextMock {
@@ -1380,7 +1449,20 @@ func TestConvertUrl(t *testing.T) {
 			api: &ApiMock{PdfMock: func(ctx context.Context, logger *zap.Logger, url, outputPath string, options PdfOptions) error {
 				return nil
 			}},
-			options:                DefaultPdfOptions(),
+			engine: &gotenberg.PdfEngineMock{
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return nil
+				},
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
+			options:    DefaultPdfOptions(),
+			pdfFormats: gotenberg.PdfFormats{PdfA: gotenberg.PdfA1b},
+			metadata: map[string]interface{}{
+				"Creator":  "foo",
+				"Producer": "bar",
+			},
 			expectError:            false,
 			expectHttpError:        false,
 			expectOutputPathsCount: 1,
@@ -1388,7 +1470,7 @@ func TestConvertUrl(t *testing.T) {
 	} {
 		t.Run(tc.scenario, func(t *testing.T) {
 			tc.ctx.SetLogger(zap.NewNop())
-			err := convertUrl(tc.ctx.Context, tc.api, tc.engine, "", tc.pdfFormats, tc.options)
+			err := convertUrl(tc.ctx.Context, tc.api, tc.engine, "", tc.options, tc.pdfFormats, tc.metadata)
 
 			if tc.expectError && err == nil {
 				t.Fatal("expected error but got none", err)

pkg/modules/exiftool/doc.go

@@ -0,0 +1,11 @@
+// Package exiftool provides an implementation of the gotenberg.PdfEngine
+// interface using the ExifTool command-line tool. This package allows for:
+//
+// 1. The reading of metadata.
+// 2. The writing of metadata.
+//
+// The path to the exiftool binary must be specified using the
+// EXIFTOOL_BIN_PATH environment variable.
+//
+// See: https://exiftool.org.
+package exiftool

pkg/modules/exiftool/exiftool.go

@@ -0,0 +1,143 @@
+package exiftool
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/barasher/go-exiftool"
+	"go.uber.org/zap"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
+)
+
+func init() {
+	gotenberg.MustRegisterModule(new(ExifTool))
+}
+
+// ExifTool abstracts the CLI tool ExifTool and implements the
+// [gotenberg.PdfEngine] interface.
+type ExifTool struct {
+	binPath string
+}
+
+// Descriptor returns [ExifTool]'s module descriptor.
+func (engine *ExifTool) Descriptor() gotenberg.ModuleDescriptor {
+	return gotenberg.ModuleDescriptor{
+		ID:  "exiftool",
+		New: func() gotenberg.Module { return new(ExifTool) },
+	}
+}
+
+// Provision sets the module properties.
+func (engine *ExifTool) Provision(ctx *gotenberg.Context) error {
+	binPath, ok := os.LookupEnv("EXIFTOOL_BIN_PATH")
+	if !ok {
+		return errors.New("EXIFTOOL_BIN_PATH environment variable is not set")
+	}
+
+	engine.binPath = binPath
+
+	return nil
+}
+
+// Validate validates the module properties.
+func (engine *ExifTool) Validate() error {
+	_, err := os.Stat(engine.binPath)
+	if os.IsNotExist(err) {
+		return fmt.Errorf("ExifTool binary path does not exist: %w", err)
+	}
+
+	return nil
+}
+
+// Merge is not available in this implementation.
+func (engine *ExifTool) Merge(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+	return fmt.Errorf("merge PDFs with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// Convert is not available in this implementation.
+func (engine *ExifTool) Convert(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+	return fmt.Errorf("convert PDF to '%+v' with ExifTool: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// ReadMetadata extracts the metadata of a given PDF file.
+func (engine *ExifTool) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	exifTool, err := exiftool.NewExiftool(exiftool.SetExiftoolBinaryPath(engine.binPath))
+	if err != nil {
+		return nil, fmt.Errorf("new ExifTool: %w", err)
+	}
+
+	defer func(exifTool *exiftool.Exiftool) {
+		err := exifTool.Close()
+		if err != nil {
+			logger.Error(fmt.Sprintf("close ExifTool: %v", err))
+		}
+	}(exifTool)
+
+	fileMetadata := exifTool.ExtractMetadata(inputPath)
+	if fileMetadata[0].Err != nil {
+		return nil, fmt.Errorf("read metadata with ExitfTool: %w", fileMetadata[0].Err)
+	}
+
+	return fileMetadata[0].Fields, nil
+}
+
+// WriteMetadata writes the metadata into a given PDF file.
+func (engine *ExifTool) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	exifTool, err := exiftool.NewExiftool(exiftool.SetExiftoolBinaryPath(engine.binPath))
+	if err != nil {
+		return fmt.Errorf("new ExifTool: %w", err)
+	}
+
+	defer func(exifTool *exiftool.Exiftool) {
+		err := exifTool.Close()
+		if err != nil {
+			logger.Error(fmt.Sprintf("close ExifTool: %v", err))
+		}
+	}(exifTool)
+
+	fileMetadata := exifTool.ExtractMetadata(inputPath)
+	if fileMetadata[0].Err != nil {
+		return fmt.Errorf("read metadata with ExitfTool: %w", fileMetadata[0].Err)
+	}
+
+	for key, value := range metadata {
+		switch val := value.(type) {
+		case string:
+			fileMetadata[0].SetString(key, val)
+		case []string:
+			fileMetadata[0].SetStrings(key, val)
+		case bool:
+			fileMetadata[0].SetString(key, fmt.Sprintf("%t", val))
+		case int:
+			fileMetadata[0].SetInt(key, int64(val))
+		case int64:
+			fileMetadata[0].SetInt(key, val)
+		case float32:
+			fileMetadata[0].SetFloat(key, float64(val))
+		case float64:
+			fileMetadata[0].SetFloat(key, val)
+		// TODO: support more complex cases, e.g., arrays and nested objects
+		// 	(limitations in underlying library).
+		default:
+			return fmt.Errorf("write PDF metadata with ExifTool: %w", gotenberg.ErrPdfEngineMetadataValueNotSupported)
+		}
+	}
+
+	exifTool.WriteMetadata(fileMetadata)
+	if fileMetadata[0].Err != nil {
+		return fmt.Errorf("write PDF metadata with ExifTool: %w", fileMetadata[0].Err)
+	}
+
+	return nil
+}
+
+// Interface guards.
+var (
+	_ gotenberg.Module      = (*ExifTool)(nil)
+	_ gotenberg.Provisioner = (*ExifTool)(nil)
+	_ gotenberg.Validator   = (*ExifTool)(nil)
+	_ gotenberg.PdfEngine   = (*ExifTool)(nil)
+)

pkg/modules/exiftool/exiftool_test.go

@@ -0,0 +1,322 @@
+package exiftool
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"reflect"
+	"testing"
+
+	"go.uber.org/zap"
+
+	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
+)
+
+func TestExifTool_Descriptor(t *testing.T) {
+	descriptor := new(ExifTool).Descriptor()
+
+	actual := reflect.TypeOf(descriptor.New())
+	expect := reflect.TypeOf(new(ExifTool))
+
+	if actual != expect {
+		t.Errorf("expected '%s' but got '%s'", expect, actual)
+	}
+}
+
+func TestExifTool_Provision(t *testing.T) {
+	engine := new(ExifTool)
+	ctx := gotenberg.NewContext(gotenberg.ParsedFlags{}, nil)
+
+	err := engine.Provision(ctx)
+	if err != nil {
+		t.Errorf("expected no error but got: %v", err)
+	}
+}
+
+func TestExifTool_Validate(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		binPath     string
+		expectError bool
+	}{
+		{
+			scenario:    "empty bin path",
+			binPath:     "",
+			expectError: true,
+		},
+		{
+			scenario:    "bin path does not exist",
+			binPath:     "/foo",
+			expectError: true,
+		},
+		{
+			scenario:    "validate success",
+			binPath:     os.Getenv("EXIFTOOL_BIN_PATH"),
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			engine := new(ExifTool)
+			engine.binPath = tc.binPath
+			err := engine.Validate()
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none")
+			}
+		})
+	}
+}
+
+func TestExiftool_Merge(t *testing.T) {
+	engine := new(ExifTool)
+	err := engine.Merge(context.Background(), zap.NewNop(), nil, "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestExiftool_Convert(t *testing.T) {
+	engine := new(ExifTool)
+	err := engine.Convert(context.Background(), zap.NewNop(), gotenberg.PdfFormats{}, "", "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestExiftool_ReadMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario       string
+		inputPath      string
+		expectMetadata map[string]interface{}
+		expectError    bool
+	}{
+		{
+			scenario:       "invalid input path",
+			inputPath:      "foo",
+			expectMetadata: nil,
+			expectError:    true,
+		},
+		{
+			scenario:  "success",
+			inputPath: "/tests/test/testdata/pdfengines/sample1.pdf",
+			expectMetadata: map[string]interface{}{
+				"FileName":          "sample1.pdf",
+				"FileTypeExtension": "pdf",
+				"MIMEType":          "application/pdf",
+				"PDFVersion":        1.4,
+				"PageCount":         float64(3),
+			},
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			engine := new(ExifTool)
+			err := engine.Provision(nil)
+			if err != nil {
+				t.Fatalf("expected error but got: %v", err)
+			}
+
+			metadata, err := engine.ReadMetadata(context.Background(), zap.NewNop(), tc.inputPath)
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none")
+			}
+
+			if tc.expectMetadata != nil && err == nil {
+				for k, v := range tc.expectMetadata {
+					if v2, ok := metadata[k]; !ok || v != v2 {
+						t.Errorf("expected entry %s with value %v to exists", k, v)
+					}
+				}
+			}
+		})
+	}
+}
+
+func TestExiftool_WriteMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario       string
+		createCopy     bool
+		inputPath      string
+		metadata       map[string]interface{}
+		expectMetadata map[string]interface{}
+		expectError    bool
+		expectedError  error
+	}{
+		{
+			scenario:    "invalid input path",
+			createCopy:  false,
+			inputPath:   "foo",
+			expectError: true,
+		},
+		{
+			scenario:   "gotenberg.ErrPdfEngineMetadataValueNotSupported",
+			createCopy: true,
+			inputPath:  "/tests/test/testdata/pdfengines/sample1.pdf",
+			metadata: map[string]interface{}{
+				"Unsupported": map[string]interface{}{},
+			},
+			expectError:   true,
+			expectedError: gotenberg.ErrPdfEngineMetadataValueNotSupported,
+		},
+		{
+			scenario:   "success",
+			createCopy: true,
+			inputPath:  "/tests/test/testdata/pdfengines/sample1.pdf",
+			metadata: map[string]interface{}{
+				"Author":       "Julien Neuhart",
+				"Copyright":    "Julien Neuhart",
+				"CreationDate": "2006-09-18T16:27:50-04:00",
+				"Creator":      "Gotenberg",
+				"Keywords": []string{
+					"first",
+					"second",
+				},
+				"Marked":     true,
+				"ModDate":    "2006-09-18T16:27:50-04:00",
+				"PDFVersion": 1.7,
+				"Producer":   "Gotenberg",
+				"Subject":    "Sample",
+				"Title":      "Sample",
+				"Trapped":    "Unknown",
+				// Those are not valid PDF metadata.
+				"int":     1,
+				"int64":   int64(2),
+				"float32": float32(2.2),
+				"float64": 3.3,
+			},
+			expectMetadata: map[string]interface{}{
+				"Author":       "Julien Neuhart",
+				"Copyright":    "Julien Neuhart",
+				"CreationDate": "2006:09:18 16:27:50-04:00",
+				"Creator":      "Gotenberg",
+				"Keywords": []interface{}{
+					"first",
+					"second",
+				},
+				"Marked":     true,
+				"ModDate":    "2006:09:18 16:27:50-04:00",
+				"PDFVersion": 1.7,
+				"Producer":   "Gotenberg",
+				"Subject":    "Sample",
+				"Title":      "Sample",
+				"Trapped":    "Unknown",
+			},
+			expectError: false,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			engine := new(ExifTool)
+			err := engine.Provision(nil)
+			if err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			var destinationPath string
+			if tc.createCopy {
+				fs := gotenberg.NewFileSystem()
+				outputDir, err := fs.MkdirAll()
+				if err != nil {
+					t.Fatalf("expected error no but got: %v", err)
+				}
+
+				defer func() {
+					err = os.RemoveAll(fs.WorkingDirPath())
+					if err != nil {
+						t.Fatalf("expected no error while cleaning up but got: %v", err)
+					}
+				}()
+
+				destinationPath = fmt.Sprintf("%s/copy_temp.pdf", outputDir)
+				source, err := os.Open(tc.inputPath)
+				if err != nil {
+					t.Fatalf("open source file: %v", err)
+				}
+
+				defer func(source *os.File) {
+					err := source.Close()
+					if err != nil {
+						t.Fatalf("close file: %v", err)
+					}
+				}(source)
+
+				destination, err := os.Create(destinationPath)
+				if err != nil {
+					t.Fatalf("create destination file: %v", err)
+				}
+
+				defer func(destination *os.File) {
+					err := destination.Close()
+					if err != nil {
+						t.Fatalf("close file: %v", err)
+					}
+				}(destination)
+
+				_, err = io.Copy(destination, source)
+				if err != nil {
+					t.Fatalf("copy source into destination: %v", err)
+				}
+			} else {
+				destinationPath = tc.inputPath
+			}
+
+			err = engine.WriteMetadata(context.Background(), zap.NewNop(), tc.metadata, destinationPath)
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none")
+			}
+
+			if tc.expectedError != nil && !errors.Is(err, tc.expectedError) {
+				t.Fatalf("expected error %v but got: %v", tc.expectedError, err)
+			}
+
+			if tc.expectError {
+				return
+			}
+
+			metadata, err := engine.ReadMetadata(context.Background(), zap.NewNop(), destinationPath)
+			if err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectMetadata != nil && err == nil {
+				for k, v := range tc.expectMetadata {
+					v2, ok := metadata[k]
+					if !ok {
+						t.Errorf("expected entry %s with value %v to exists, but got none", k, v)
+						continue
+					}
+
+					switch v2.(type) {
+					case []interface{}:
+						for i, entry := range v.([]interface{}) {
+							if entry != v2.([]interface{})[i] {
+								t.Errorf("expected entry %s to contain value %v, but got %v", k, entry, v2.([]interface{})[i])
+							}
+						}
+					default:
+						if v != v2 {
+							t.Errorf("expected entry %s with value %v to exists, but got %v", k, v, v2)
+						}
+					}
+				}
+			}
+		})
+	}
+}

pkg/modules/libreoffice/api/api.go

@@ -50,6 +50,10 @@ type Options struct {
 	// Optional.
 	PageRanges string
 
+	// ExportFormFields allows to... export form fields in the resulting PDF.
+	// Optional.
+	ExportFormFields bool
+
 	// PdfFormats allows to convert the resulting PDF to PDF/A-1b, PDF/A-2b,
 	// PDF/A-3b and PDF/UA.
 	// Optional.
@@ -266,14 +270,25 @@ func (a *Api) Pdf(ctx context.Context, logger *zap.Logger, inputPath, outputPath
 // FIXME: don't care, take all on the route level?
 func (a *Api) Extensions() []string {
 	return []string{
+		".123",
+		".602",
+		".abw",
 		".bib",
 		".bmp",
+		".cdr",
+		".cgm",
+		".cmx",
 		".csv",
+		".cwk",
 		".dbf",
 		".dif",
 		".doc",
+		".docm",
 		".docx",
+		".dot",
+		".dotm",
 		".dotx",
+		".dxf",
 		".emf",
 		".eps",
 		".epub",
@@ -281,35 +296,52 @@ func (a *Api) Extensions() []string {
 		".fodp",
 		".fods",
 		".fodt",
+		".fopd",
 		".gif",
+		".htm",
 		".html",
+		".hwp",
 		".jpeg",
 		".jpg",
 		".key",
 		".ltx",
+		".lwp",
+		".mcw",
 		".met",
+		".mml",
+		".mw",
+		".numbers",
 		".odd",
 		".odg",
+		".odm",
 		".odp",
 		".ods",
 		".odt",
 		".otg",
+		".oth",
+		".otp",
 		".ots",
 		".ott",
 		".pages",
 		".pbm",
+		".pcd",
 		".pct",
+		".pcx",
 		".pdb",
 		".pdf",
 		".pgm",
 		".png",
 		".pot",
 		".potm",
+		".potx",
 		".ppm",
 		".pps",
 		".ppt",
+		".pptm",
 		".pptx",
+		".psd",
 		".psw",
+		".pub",
 		".pwp",
 		".pxl",
 		".ras",
@@ -317,8 +349,11 @@ func (a *Api) Extensions() []string {
 		".sda",
 		".sdc",
 		".sdd",
+		".sdp",
 		".sdw",
+		".sgl",
 		".slk",
+		".smf",
 		".stc",
 		".std",
 		".sti",
@@ -328,25 +363,43 @@ func (a *Api) Extensions() []string {
 		".swf",
 		".sxc",
 		".sxd",
+		".sxg",
 		".sxi",
+		".sxm",
 		".sxw",
-		".sxw",
+		".tga",
 		".tif",
 		".tiff",
 		".txt",
+		".uof",
 		".uop",
 		".uos",
 		".uot",
+		".vdx",
 		".vor",
+		".vsd",
+		".vsdm",
+		".vsdx",
+		".wb2",
+		".wk1",
+		".wks",
 		".wmf",
+		".wpd",
+		".wpg",
 		".wps",
+		".xbm",
 		".xhtml",
 		".xls",
+		".xlsb",
+		".xlsm",
 		".xlsx",
 		".xlt",
+		".xltm",
 		".xltx",
+		".xlw",
 		".xml",
 		".xpm",
+		".zabw",
 	}
 }
 

pkg/modules/libreoffice/api/api_test.go

@@ -450,7 +450,7 @@ func TestApi_Extensions(t *testing.T) {
 	extensions := a.Extensions()
 
 	actual := len(extensions)
-	expect := 81
+	expect := 130
 
 	if actual != expect {
 		t.Errorf("expected %d extensions, but got %d", expect, actual)

pkg/modules/libreoffice/api/libreoffice.go

@@ -273,6 +273,10 @@ func (p *libreOfficeProcess) pdf(ctx context.Context, logger *zap.Logger, inputP
 		args = append(args, "--export", fmt.Sprintf("PageRange=%s", options.PageRanges))
 	}
 
+	if !options.ExportFormFields {
+		args = append(args, "--export", "ExportFormFields=false")
+	}
+
 	switch options.PdfFormats.PdfA {
 	case "":
 	case gotenberg.PdfA1b:

pkg/modules/libreoffice/api/libreoffice_test.go

@@ -364,6 +364,35 @@ func TestLibreOfficeProcess_pdf(t *testing.T) {
 			start:        true,
 			expectError:  false,
 		},
+		{
+			scenario: "success (disable form fields)",
+			libreOffice: newLibreOfficeProcess(
+				libreOfficeArguments{
+					binPath:      os.Getenv("LIBREOFFICE_BIN_PATH"),
+					unoBinPath:   os.Getenv("UNOCONVERTER_BIN_PATH"),
+					startTimeout: 5 * time.Second,
+				},
+			),
+			fs: func() *gotenberg.FileSystem {
+				fs := gotenberg.NewFileSystem()
+
+				err := os.MkdirAll(fs.WorkingDirPath(), 0o755)
+				if err != nil {
+					t.Fatalf(fmt.Sprintf("expected no error but got: %v", err))
+				}
+
+				err = os.WriteFile(fmt.Sprintf("%s/document.txt", fs.WorkingDirPath()), []byte("DisableFormFields"), 0o755)
+				if err != nil {
+					t.Fatalf("expected no error but got: %v", err)
+				}
+
+				return fs
+			}(),
+			options:      Options{ExportFormFields: false},
+			cancelledCtx: false,
+			start:        true,
+			expectError:  false,
+		},
 		{
 			scenario: "success (page ranges)",
 			libreOffice: newLibreOfficeProcess(

pkg/modules/libreoffice/pdfengine/doc.go

@@ -1,4 +1,6 @@
 // Package pdfengine provides a module which interacts with LibreOffice via the
 // UNO (Universal Network Objects) API and implements the gotenberg.PdfEngine
-// interface.
+// interface. This package allows for:
+//
+// 1. The conversion to specific PDF formats.
 package pdfengine

pkg/modules/libreoffice/pdfengine/pdfengine.go

@@ -71,6 +71,16 @@ func (engine *LibreOfficePdfEngine) Convert(ctx context.Context, logger *zap.Log
 	return fmt.Errorf("convert PDF to '%+v' with LibreOffice: %w", formats, err)
 }
 
+// ReadMetadata is not available in this implementation.
+func (engine *LibreOfficePdfEngine) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	return nil, fmt.Errorf("read PDF metadata with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// WriteMetadata is not available in this implementation.
+func (engine *LibreOfficePdfEngine) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	return fmt.Errorf("write PDF metadata with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*LibreOfficePdfEngine)(nil)

pkg/modules/libreoffice/pdfengine/pdfengine_test.go

@@ -166,3 +166,21 @@ func TestLibreOfficePdfEngine_Convert(t *testing.T) {
 		})
 	}
 }
+
+func TestLibreOfficePdfEngine_ReadMetadata(t *testing.T) {
+	engine := new(LibreOfficePdfEngine)
+	_, err := engine.ReadMetadata(context.Background(), zap.NewNop(), "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestLibreOfficePdfEngine_WriteMetadata(t *testing.T) {
+	engine := new(LibreOfficePdfEngine)
+	err := engine.WriteMetadata(context.Background(), zap.NewNop(), nil, "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}

pkg/modules/libreoffice/routes.go

@@ -1,6 +1,7 @@
 package libreoffice
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
@@ -27,20 +28,32 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				inputPaths       []string
 				landscape        bool
 				nativePageRanges string
+				exportFormFields bool
 				pdfa             string
 				pdfua            bool
 				nativePdfFormats bool
 				merge            bool
+				metadata         map[string]interface{}
 			)
 
 			err := ctx.FormData().
 				MandatoryPaths(libreOffice.Extensions(), &inputPaths).
 				Bool("landscape", &landscape, false).
 				String("nativePageRanges", &nativePageRanges, "").
+				Bool("exportFormFields", &exportFormFields, true).
 				String("pdfa", &pdfa, "").
 				Bool("pdfua", &pdfua, false).
 				Bool("nativePdfFormats", &nativePdfFormats, true).
 				Bool("merge", &merge, false).
+				Custom("metadata", func(value string) error {
+					if len(value) > 0 {
+						err := json.Unmarshal([]byte(value), &metadata)
+						if err != nil {
+							return fmt.Errorf("unmarshal metadata: %w", err)
+						}
+					}
+					return nil
+				}).
 				Validate()
 			if err != nil {
 				return fmt.Errorf("validate form data: %w", err)
@@ -56,8 +69,9 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 			for i, inputPath := range inputPaths {
 				outputPaths[i] = ctx.GeneratePath(".pdf")
 				options := libreofficeapi.Options{
-					Landscape:  landscape,
-					PageRanges: nativePageRanges,
+					Landscape:        landscape,
+					PageRanges:       nativePageRanges,
+					ExportFormFields: exportFormFields,
 				}
 
 				if nativePdfFormats {
@@ -87,8 +101,7 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				}
 			}
 
-			// So far so good, let's check if we have to merge the PDFs. Quick
-			// win: if there is only one PDF, skip this step.
+			// So far so good, let's check if we have to merge the PDFs.
 			if len(outputPaths) > 1 && merge {
 				outputPath := ctx.GeneratePath(".pdf")
 
@@ -97,34 +110,12 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 					return fmt.Errorf("merge PDFs: %w", err)
 				}
 
-				// Now, let's check if the client want to convert this
-				// resulting PDF to specific PDF formats.
-				zeroValued := gotenberg.PdfFormats{}
-				if !nativePdfFormats && pdfFormats != zeroValued {
-					convertInputPath := outputPath
-					convertOutputPath := ctx.GeneratePath(".pdf")
-
-					err = engine.Convert(ctx, ctx.Log(), pdfFormats, convertInputPath, convertOutputPath)
-					if err != nil {
-						return fmt.Errorf("convert PDF: %w", err)
-					}
-
-					// Important: the output path is now the converted file.
-					outputPath = convertOutputPath
-				}
-
-				// Last but not least, add the output path to the context so that
-				// the API is able to send it as a response to the client.
-				err = ctx.AddOutputPaths(outputPath)
-				if err != nil {
-					return fmt.Errorf("add output path: %w", err)
-				}
-
-				return nil
+				// Only one output path.
+				outputPaths = []string{outputPath}
 			}
 
-			// Ok, we don't have to merge the PDFs. Let's check if the client
-			// want to convert each PDF to a specific PDF format.
+			// Let's check if the client want to convert each PDF to a specific
+			// PDF format.
 			zeroValued := gotenberg.PdfFormats{}
 			if !nativePdfFormats && pdfFormats != zeroValued {
 				convertOutputPaths := make([]string, len(outputPaths))
@@ -143,6 +134,16 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				outputPaths = convertOutputPaths
 			}
 
+			// Writes and potentially overrides metadata entries, if any.
+			if len(metadata) > 0 {
+				for _, outputPath := range outputPaths {
+					err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
+					if err != nil {
+						return fmt.Errorf("write metadata: %w", err)
+					}
+				}
+			}
+
 			if len(outputPaths) > 1 {
 				// If .zip archive, document.docx -> document.docx.pdf.
 				for i, inputPath := range inputPaths {

pkg/modules/libreoffice/routes_test.go

@@ -39,6 +39,28 @@ func TestConvertRoute(t *testing.T) {
 			expectHttpStatus:       http.StatusBadRequest,
 			expectOutputPathsCount: 0,
 		},
+		{
+			scenario: "invalid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx": "/document.docx",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"foo",
+					},
+				})
+				return ctx
+			}(),
+			libreOffice: &libreofficeapi.ApiMock{ExtensionsMock: func() []string {
+				return []string{".docx"}
+			}},
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
 		{
 			scenario: "ErrPdfFormatNotSupported (nativePdfFormats)",
 			ctx: func() *api.ContextMock {
@@ -110,7 +132,39 @@ func TestConvertRoute(t *testing.T) {
 			expectOutputPathsCount: 0,
 		},
 		{
-			scenario: "PDF engine convert error (single file)",
+			scenario: "PDF engine merge error",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx":  "/document.docx",
+					"document2.docx": "/document2.docx",
+				})
+				ctx.SetValues(map[string][]string{
+					"merge": {
+						"true",
+					},
+				})
+				return ctx
+			}(),
+			libreOffice: &libreofficeapi.ApiMock{
+				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
+					return nil
+				},
+				ExtensionsMock: func() []string {
+					return []string{".docx"}
+				},
+			},
+			engine: &gotenberg.PdfEngineMock{
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "PDF engine convert error",
 			ctx: func() *api.ContextMock {
 				ctx := &api.ContextMock{Context: new(api.Context)}
 				ctx.SetFiles(map[string]string{
@@ -144,13 +198,17 @@ func TestConvertRoute(t *testing.T) {
 			expectOutputPathsCount: 0,
 		},
 		{
-			scenario: "cannot add output paths (single file)",
+			scenario: "PDF engine write metadata error",
 			ctx: func() *api.ContextMock {
 				ctx := &api.ContextMock{Context: new(api.Context)}
 				ctx.SetFiles(map[string]string{
 					"document.docx": "/document.docx",
 				})
-				ctx.SetCancelled(true)
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
 				return ctx
 			}(),
 			libreOffice: &libreofficeapi.ApiMock{
@@ -161,31 +219,15 @@ func TestConvertRoute(t *testing.T) {
 					return []string{".docx"}
 				},
 			},
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return errors.New("foo")
+				},
+			},
 			expectError:            true,
 			expectHttpError:        false,
 			expectOutputPathsCount: 0,
 		},
-		{
-			scenario: "success (single file)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx": "/document.docx",
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 1,
-		},
 		{
 			scenario: "cannot rename many files",
 			ctx: func() *api.ContextMock {
@@ -212,6 +254,78 @@ func TestConvertRoute(t *testing.T) {
 			expectHttpError:        false,
 			expectOutputPathsCount: 0,
 		},
+		{
+			scenario: "cannot add output paths",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx": "/document.docx",
+				})
+				ctx.SetCancelled(true)
+				return ctx
+			}(),
+			libreOffice: &libreofficeapi.ApiMock{
+				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
+					return nil
+				},
+				ExtensionsMock: func() []string {
+					return []string{".docx"}
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "success (single file)",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx":  "/document.docx",
+					"document2.docx": "/document2.docx",
+				})
+				ctx.SetValues(map[string][]string{
+					"merge": {
+						"true",
+					},
+					"pdfa": {
+						gotenberg.PdfA1b,
+					},
+					"pdfua": {
+						"true",
+					},
+					"nativePdfFormats": {
+						"false",
+					},
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
+				return ctx
+			}(),
+			libreOffice: &libreofficeapi.ApiMock{
+				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
+					return nil
+				},
+				ExtensionsMock: func() []string {
+					return []string{".docx"}
+				},
+			},
+			engine: &gotenberg.PdfEngineMock{
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return nil
+				},
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return nil
+				},
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
+			expectError:            false,
+			expectHttpError:        false,
+			expectOutputPathsCount: 1,
+		},
 		{
 			scenario: "success (many files)",
 			ctx: func() *api.ContextMock {
@@ -221,6 +335,20 @@ func TestConvertRoute(t *testing.T) {
 					"document2.docx": "/document2.docx",
 					"document2.doc":  "/document2.doc",
 				})
+				ctx.SetValues(map[string][]string{
+					"pdfa": {
+						gotenberg.PdfA1b,
+					},
+					"pdfua": {
+						"true",
+					},
+					"nativePdfFormats": {
+						"false",
+					},
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
 				ctx.SetPathRename(&gotenberg.PathRenameMock{RenameMock: func(oldpath, newpath string) error {
 					return nil
 				}})
@@ -234,60 +362,28 @@ func TestConvertRoute(t *testing.T) {
 					return []string{".docx", ".doc"}
 				},
 			},
+			engine: &gotenberg.PdfEngineMock{
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return nil
+				},
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return nil
+				},
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
 			expectError:            false,
 			expectHttpError:        false,
 			expectOutputPathsCount: 3,
 			expectOutputPaths:      []string{"/document.docx.pdf", "/document2.docx.pdf", "/document2.doc.pdf"},
 		},
 		{
-			scenario: "success with non-native PDF/A & PDF/UA (many files)",
+			scenario: "success with native PDF/A & PDF/UA",
 			ctx: func() *api.ContextMock {
 				ctx := &api.ContextMock{Context: new(api.Context)}
 				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"pdfa": {
-						gotenberg.PdfA1b,
-					},
-					"pdfua": {
-						"true",
-					},
-					"nativePdfFormats": {
-						"false",
-					},
-				})
-				ctx.SetPathRename(&gotenberg.PathRenameMock{RenameMock: func(oldpath, newpath string) error {
-					return nil
-				}})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 2,
-			expectOutputPaths:      []string{"/document.docx.pdf", "/document2.docx.pdf"},
-		},
-		{
-			scenario: "success with native PDF/A & PDF/UA (many files)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
+					"document.docx": "/document.docx",
 				})
 				ctx.SetValues(map[string][]string{
 					"pdfa": {
@@ -297,9 +393,6 @@ func TestConvertRoute(t *testing.T) {
 						"true",
 					},
 				})
-				ctx.SetPathRename(&gotenberg.PathRenameMock{RenameMock: func(oldpath, newpath string) error {
-					return nil
-				}})
 				return ctx
 			}(),
 			libreOffice: &libreofficeapi.ApiMock{
@@ -310,238 +403,6 @@ func TestConvertRoute(t *testing.T) {
 					return []string{".docx"}
 				},
 			},
-			engine: &gotenberg.PdfEngineMock{
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 2,
-			expectOutputPaths:      []string{"/document.docx.pdf", "/document2.docx.pdf"},
-		},
-		{
-			scenario: "merge error",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return errors.New("foo")
-				},
-			},
-			expectError:            true,
-			expectHttpError:        false,
-			expectOutputPathsCount: 0,
-		},
-		{
-			scenario: "PDF engine convert error (merge)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-					"pdfa": {
-						gotenberg.PdfA1b,
-					},
-					"nativePdfFormats": {
-						"false",
-					},
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return errors.New("foo")
-				},
-			},
-			expectError:            true,
-			expectHttpError:        false,
-			expectOutputPathsCount: 0,
-		},
-		{
-			scenario: "cannot add output paths (merge)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-				})
-				ctx.SetCancelled(true)
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            true,
-			expectHttpError:        false,
-			expectOutputPathsCount: 0,
-		},
-		{
-			scenario: "success (merge)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 1,
-		},
-		{
-			scenario: "success with non-native PDF/A & PDF/UA (merge)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-					"pdfa": {
-						gotenberg.PdfA1b,
-					},
-					"pdfua": {
-						"true",
-					},
-					"nativePdfFormats": {
-						"false",
-					},
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 1,
-		},
-		{
-			scenario: "success with non-native PDF/A & PDF/UA (merge)",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"document.docx":  "/document.docx",
-					"document2.docx": "/document2.docx",
-				})
-				ctx.SetValues(map[string][]string{
-					"merge": {
-						"true",
-					},
-					"pdfa": {
-						gotenberg.PdfA1b,
-					},
-					"pdfua": {
-						"true",
-					},
-					"nativePdfFormats": {
-						"false",
-					},
-				})
-				return ctx
-			}(),
-			libreOffice: &libreofficeapi.ApiMock{
-				PdfMock: func(ctx context.Context, logger *zap.Logger, inputPath, outputPath string, options libreofficeapi.Options) error {
-					return nil
-				},
-				ExtensionsMock: func() []string {
-					return []string{".docx"}
-				},
-			},
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return nil
-				},
-			},
 			expectError:            false,
 			expectHttpError:        false,
 			expectOutputPathsCount: 1,

pkg/modules/pdfcpu/doc.go

@@ -1,6 +1,7 @@
 // Package pdfcpu provides an implementation of the gotenberg.PdfEngine
-// interface using the pdfcpu library. This package allows for the merging of
-// PDF files but does not support conversion to specific PDF formats.
+// interface using the pdfcpu library. This package allows for:
+//
+// 1. The merging of PDF files.
 //
 // See: https://github.com/pdfcpu/pdfcpu.
 package pdfcpu

pkg/modules/pdfcpu/pdfcpu.go

@@ -54,6 +54,16 @@ func (engine *PdfCpu) Convert(ctx context.Context, logger *zap.Logger, formats g
 	return fmt.Errorf("convert PDF to '%+v' with PDFcpu: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// ReadMetadata is not available in this implementation.
+func (engine *PdfCpu) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	return nil, fmt.Errorf("read PDF metadata with PDFcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// WriteMetadata is not available in this implementation.
+func (engine *PdfCpu) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	return fmt.Errorf("write PDF metadata with PDFcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*PdfCpu)(nil)

pkg/modules/pdfcpu/pdfcpu_test.go

@@ -102,3 +102,21 @@ func TestPdfCpu_Convert(t *testing.T) {
 		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
 	}
 }
+
+func TestLibreOfficePdfEngine_ReadMetadata(t *testing.T) {
+	engine := new(PdfCpu)
+	_, err := engine.ReadMetadata(context.Background(), zap.NewNop(), "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestLibreOfficePdfEngine_WriteMetadata(t *testing.T) {
+	engine := new(PdfCpu)
+	err := engine.WriteMetadata(context.Background(), zap.NewNop(), nil, "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}

pkg/modules/pdfengines/multi.go

@@ -3,6 +3,7 @@ package pdfengines
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"go.uber.org/multierr"
 	"go.uber.org/zap"
@@ -70,6 +71,65 @@ func (multi *multiPdfEngines) Convert(ctx context.Context, logger *zap.Logger, f
 	return fmt.Errorf("convert PDF to '%+v' with multi PDF engines: %w", formats, err)
 }
 
+type readMetadataResult struct {
+	metadata map[string]interface{}
+	err      error
+}
+
+func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	var err error
+	var mu sync.Mutex // to safely append errors.
+
+	resultChan := make(chan readMetadataResult, len(multi.engines))
+
+	for _, engine := range multi.engines {
+		go func(engine gotenberg.PdfEngine) {
+			metadata, err := engine.ReadMetadata(ctx, logger, inputPath)
+			resultChan <- readMetadataResult{metadata: metadata, err: err}
+		}(engine)
+	}
+
+	for range multi.engines {
+		select {
+		case result := <-resultChan:
+			if result.err != nil {
+				mu.Lock()
+				err = multierr.Append(err, result.err)
+				mu.Unlock()
+			} else {
+				return result.metadata, nil
+			}
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		}
+	}
+
+	return nil, fmt.Errorf("read PDF metadata with multi PDF engines: %w", err)
+}
+
+func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	var err error
+	errChan := make(chan error, 1)
+
+	for _, engine := range multi.engines {
+		go func(engine gotenberg.PdfEngine) {
+			errChan <- engine.WriteMetadata(ctx, logger, metadata, inputPath)
+		}(engine)
+
+		select {
+		case writeMetadataErr := <-errChan:
+			errored := multierr.AppendInto(&err, writeMetadataErr)
+			if !errored {
+				return nil
+			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+
+	return fmt.Errorf("write PDF metadata with multi PDF engines: %w", err)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.PdfEngine = (*multiPdfEngines)(nil)

pkg/modules/pdfengines/multi_test.go

@@ -177,3 +177,169 @@ func TestMultiPdfEngines_Convert(t *testing.T) {
 		})
 	}
 }
+
+func TestMultiPdfEngines_ReadMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		engine      *multiPdfEngines
+		ctx         context.Context
+		expectError bool
+	}{
+		{
+			scenario: "nominal behavior",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return make(map[string]interface{}), nil
+					},
+				},
+			),
+			ctx: context.Background(),
+		},
+		{
+			scenario: "at least one engine does not return an error",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return nil, errors.New("foo")
+					},
+				},
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return make(map[string]interface{}), nil
+					},
+				},
+			),
+			ctx: context.Background(),
+		},
+		{
+			scenario: "all engines return an error",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return nil, errors.New("foo")
+					},
+				},
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return nil, errors.New("foo")
+					},
+				},
+			),
+			ctx:         context.Background(),
+			expectError: true,
+		},
+		{
+			scenario: "context expired",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+						return make(map[string]interface{}), nil
+					},
+				},
+			),
+			ctx: func() context.Context {
+				ctx, cancel := context.WithCancel(context.Background())
+				cancel()
+
+				return ctx
+			}(),
+			expectError: true,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			_, err := tc.engine.ReadMetadata(tc.ctx, zap.NewNop(), "")
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none")
+			}
+		})
+	}
+}
+
+func TestMultiPdfEngines_WriteMetadata(t *testing.T) {
+	for _, tc := range []struct {
+		scenario    string
+		engine      *multiPdfEngines
+		ctx         context.Context
+		expectError bool
+	}{
+		{
+			scenario: "nominal behavior",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return nil
+					},
+				},
+			),
+			ctx: context.Background(),
+		},
+		{
+			scenario: "at least one engine does not return an error",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return errors.New("foo")
+					},
+				},
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return nil
+					},
+				},
+			),
+			ctx: context.Background(),
+		},
+		{
+			scenario: "all engines return an error",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return errors.New("foo")
+					},
+				},
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return errors.New("foo")
+					},
+				},
+			),
+			ctx:         context.Background(),
+			expectError: true,
+		},
+		{
+			scenario: "context expired",
+			engine: newMultiPdfEngines(
+				&gotenberg.PdfEngineMock{
+					WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+						return nil
+					},
+				},
+			),
+			ctx: func() context.Context {
+				ctx, cancel := context.WithCancel(context.Background())
+				cancel()
+
+				return ctx
+			}(),
+			expectError: true,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			err := tc.engine.WriteMetadata(tc.ctx, zap.NewNop(), nil, "")
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none")
+			}
+		})
+	}
+}

pkg/modules/pdfengines/pdfengines.go

@@ -168,6 +168,8 @@ func (mod *PdfEngines) Routes() ([]api.Route, error) {
 	return []api.Route{
 		mergeRoute(engine),
 		convertRoute(engine),
+		readMetadataRoute(engine),
+		writeMetadataRoute(engine),
 	}, nil
 }
 

pkg/modules/pdfengines/pdfengines_test.go

@@ -312,7 +312,7 @@ func TestPdfEngines_Routes(t *testing.T) {
 	}{
 		{
 			scenario:      "routes not disabled",
-			expectRoutes:  2,
+			expectRoutes:  4,
 			disableRoutes: false,
 		},
 		{

pkg/modules/pdfengines/routes.go

@@ -1,9 +1,11 @@
 package pdfengines
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
+	"path/filepath"
 
 	"github.com/labstack/echo/v4"
 
@@ -25,12 +27,22 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 				inputPaths []string
 				pdfa       string
 				pdfua      bool
+				metadata   map[string]interface{}
 			)
 
 			err := ctx.FormData().
 				MandatoryPaths([]string{".pdf"}, &inputPaths).
 				String("pdfa", &pdfa, "").
 				Bool("pdfua", &pdfua, false).
+				Custom("metadata", func(value string) error {
+					if len(value) > 0 {
+						err := json.Unmarshal([]byte(value), &metadata)
+						if err != nil {
+							return fmt.Errorf("unmarshal metadata: %w", err)
+						}
+					}
+					return nil
+				}).
 				Validate()
 			if err != nil {
 				return fmt.Errorf("validate form data: %w", err)
@@ -66,6 +78,14 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 				outputPath = convertOutputPath
 			}
 
+			// Writes and potentially overrides metadata entries, if any.
+			if len(metadata) > 0 {
+				err = engine.WriteMetadata(ctx, ctx.Log(), metadata, outputPath)
+				if err != nil {
+					return fmt.Errorf("write metadata: %w", err)
+				}
+			}
+
 			// Last but not least, add the output path to the context so that
 			// the API is able to send it as a response to the client.
 			err = ctx.AddOutputPaths(outputPath)
@@ -78,8 +98,8 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 	}
 }
 
-// convertRoute returns an [api.Route] which can convert a PDF to a specific
-// PDF format.
+// convertRoute returns an [api.Route] which can convert PDFs to a specific ODF
+// format.
 func convertRoute(engine gotenberg.PdfEngine) api.Route {
 	return api.Route{
 		Method:      http.MethodPost,
@@ -152,3 +172,98 @@ func convertRoute(engine gotenberg.PdfEngine) api.Route {
 		},
 	}
 }
+
+// readMetadataRoute returns an [api.Route] which returns the metadata of PDFs.
+func readMetadataRoute(engine gotenberg.PdfEngine) api.Route {
+	return api.Route{
+		Method:      http.MethodPost,
+		Path:        "/forms/pdfengines/metadata/read",
+		IsMultipart: true,
+		Handler: func(c echo.Context) error {
+			ctx := c.Get("context").(*api.Context)
+
+			// Let's get the data from the form and validate them.
+			var inputPaths []string
+
+			err := ctx.FormData().
+				MandatoryPaths([]string{".pdf"}, &inputPaths).
+				Validate()
+			if err != nil {
+				return fmt.Errorf("validate form data: %w", err)
+			}
+
+			// Alright, let's read the metadata.
+			res := make(map[string]map[string]interface{}, len(inputPaths))
+			for _, inputPath := range inputPaths {
+				metadata, err := engine.ReadMetadata(ctx, ctx.Log(), inputPath)
+				if err != nil {
+					return fmt.Errorf("read metadata: %w", err)
+				}
+
+				res[filepath.Base(inputPath)] = metadata
+			}
+
+			err = c.JSON(http.StatusOK, res)
+			if err != nil {
+				return fmt.Errorf("return JSON response: %w", err)
+			}
+
+			return api.ErrNoOutputFile
+		},
+	}
+}
+
+// writeMetadataRoute returns an [api.Route] which can write metadata into
+// PDFs.
+func writeMetadataRoute(engine gotenberg.PdfEngine) api.Route {
+	return api.Route{
+		Method:      http.MethodPost,
+		Path:        "/forms/pdfengines/metadata/write",
+		IsMultipart: true,
+		Handler: func(c echo.Context) error {
+			ctx := c.Get("context").(*api.Context)
+
+			// Let's get the data from the form and validate them.
+			var (
+				inputPaths []string
+				metadata   map[string]interface{}
+			)
+
+			err := ctx.FormData().
+				MandatoryPaths([]string{".pdf"}, &inputPaths).
+				MandatoryCustom("metadata", func(value string) error {
+					if len(value) > 0 {
+						err := json.Unmarshal([]byte(value), &metadata)
+						if err != nil {
+							return fmt.Errorf("unmarshal metadata: %w", err)
+						}
+					}
+					if len(metadata) == 0 {
+						return errors.New("no metadata")
+					}
+					return nil
+				}).
+				Validate()
+			if err != nil {
+				return fmt.Errorf("validate form data: %w", err)
+			}
+
+			// Alright, let's convert the PDFs.
+			for _, inputPath := range inputPaths {
+				err = engine.WriteMetadata(ctx, ctx.Log(), metadata, inputPath)
+				if err != nil {
+					return fmt.Errorf("write metadata: %w", err)
+				}
+			}
+
+			// Last but not least, add the output paths to the context so that
+			// the API is able to send them as a response to the client.
+			err = ctx.AddOutputPaths(inputPaths...)
+			if err != nil {
+				return fmt.Errorf("add output paths: %w", err)
+			}
+
+			return nil
+		},
+	}
+}

pkg/modules/pdfengines/routes_test.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"errors"
 	"net/http"
+	"net/http/httptest"
 	"slices"
+	"strings"
 	"testing"
 
 	"github.com/labstack/echo/v4"
@@ -33,7 +35,27 @@ func TestMergeHandler(t *testing.T) {
 			expectOutputPathsCount: 0,
 		},
 		{
-			scenario: "error from PDF engine",
+			scenario: "invalid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf":  "/file.pdf",
+					"file2.pdf": "/file2.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"foo",
+					},
+				})
+				return ctx
+			}(),
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "PDF engine merge error",
 			ctx: func() *api.ContextMock {
 				ctx := &api.ContextMock{Context: new(api.Context)}
 				ctx.SetFiles(map[string]string{
@@ -51,6 +73,60 @@ func TestMergeHandler(t *testing.T) {
 			expectHttpError:        false,
 			expectOutputPathsCount: 0,
 		},
+		{
+			scenario: "PDF engine convert error",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf":  "/file.pdf",
+					"file2.pdf": "/file2.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"pdfa": {
+						gotenberg.PdfA1b,
+					},
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return nil
+				},
+				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "PDF engine write metadata error",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf":  "/file.pdf",
+					"file2.pdf": "/file2.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
+					return nil
+				},
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
 		{
 			scenario: "cannot add output paths",
 			ctx: func() *api.ContextMock {
@@ -73,25 +149,6 @@ func TestMergeHandler(t *testing.T) {
 		},
 		{
 			scenario: "success",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"file.pdf":  "/file.pdf",
-					"file2.pdf": "/file2.pdf",
-				})
-				return ctx
-			}(),
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
-					return nil
-				},
-			},
-			expectError:            false,
-			expectHttpError:        false,
-			expectOutputPathsCount: 1,
-		},
-		{
-			scenario: "error from PDF engine (convert)",
 			ctx: func() *api.ContextMock {
 				ctx := &api.ContextMock{Context: new(api.Context)}
 				ctx.SetFiles(map[string]string{
@@ -102,6 +159,9 @@ func TestMergeHandler(t *testing.T) {
 					"pdfa": {
 						gotenberg.PdfA1b,
 					},
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
 				})
 				return ctx
 			}(),
@@ -110,36 +170,9 @@ func TestMergeHandler(t *testing.T) {
 					return nil
 				},
 				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
-					return errors.New("foo")
-				},
-			},
-			expectError:            true,
-			expectHttpError:        false,
-			expectOutputPathsCount: 0,
-		},
-		{
-			scenario: "success with PDF/A & PDF/UA form fields",
-			ctx: func() *api.ContextMock {
-				ctx := &api.ContextMock{Context: new(api.Context)}
-				ctx.SetFiles(map[string]string{
-					"file.pdf":  "/file.pdf",
-					"file2.pdf": "/file2.pdf",
-				})
-				ctx.SetValues(map[string][]string{
-					"pdfa": {
-						gotenberg.PdfA1b,
-					},
-					"pdfua": {
-						"true",
-					},
-				})
-				return ctx
-			}(),
-			engine: &gotenberg.PdfEngineMock{
-				MergeMock: func(ctx context.Context, logger *zap.Logger, inputPaths []string, outputPath string) error {
 					return nil
 				},
-				ConvertMock: func(ctx context.Context, logger *zap.Logger, formats gotenberg.PdfFormats, inputPath, outputPath string) error {
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
 					return nil
 				},
 			},
@@ -401,3 +434,295 @@ func TestConvertHandler(t *testing.T) {
 		})
 	}
 }
+
+func TestReadMetadataHandler(t *testing.T) {
+	for _, tc := range []struct {
+		scenario         string
+		ctx              *api.ContextMock
+		engine           gotenberg.PdfEngine
+		expectError      bool
+		expectedError    error
+		expectHttpError  bool
+		expectHttpStatus int
+		expectedJson     string
+	}{
+		{
+			scenario:         "missing at least one mandatory file",
+			ctx:              &api.ContextMock{Context: new(api.Context)},
+			expectError:      true,
+			expectHttpError:  true,
+			expectHttpStatus: http.StatusBadRequest,
+		},
+		{
+			scenario: "error from PDF engine",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+					return nil, errors.New("foo")
+				},
+			},
+			expectError:     true,
+			expectHttpError: false,
+		},
+		{
+			scenario: "success",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				ReadMetadataMock: func(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+					return map[string]interface{}{
+						"foo": "bar",
+						"bar": "foo",
+					}, nil
+				},
+			},
+			expectError:     true,
+			expectedError:   api.ErrNoOutputFile,
+			expectHttpError: false,
+			expectedJson:    `{"file.pdf":{"bar":"foo","foo":"bar"}}`,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			tc.ctx.SetLogger(zap.NewNop())
+			req := httptest.NewRequest(http.MethodPost, "/forms/pdfengines/metadata/read", nil)
+			rec := httptest.NewRecorder()
+			c := echo.New().NewContext(req, rec)
+			c.Set("context", tc.ctx.Context)
+
+			err := readMetadataRoute(tc.engine).Handler(c)
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none", err)
+			}
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			var httpErr api.HttpError
+			isHttpError := errors.As(err, &httpErr)
+
+			if tc.expectHttpError && !isHttpError {
+				t.Errorf("expected an HTTP error but got: %v", err)
+			}
+
+			if !tc.expectHttpError && isHttpError {
+				t.Errorf("expected no HTTP error but got one: %v", httpErr)
+			}
+
+			if tc.expectedError != nil && !errors.Is(err, tc.expectedError) {
+				t.Fatalf("expected error %v but got: %v", tc.expectedError, err)
+			}
+
+			if err != nil && tc.expectHttpError && isHttpError {
+				status, _ := httpErr.HttpError()
+				if status != tc.expectHttpStatus {
+					t.Errorf("expected %d as HTTP status code but got %d", tc.expectHttpStatus, status)
+				}
+			}
+
+			if tc.expectedJson != "" && tc.expectedJson != strings.TrimSpace(rec.Body.String()) {
+				t.Errorf("expected '%s' as HTTP response but got '%s'", tc.expectedJson, strings.TrimSpace(rec.Body.String()))
+			}
+		})
+	}
+}
+
+func TestWriteMetadataHandler(t *testing.T) {
+	for _, tc := range []struct {
+		scenario               string
+		ctx                    *api.ContextMock
+		engine                 gotenberg.PdfEngine
+		expectError            bool
+		expectHttpError        bool
+		expectHttpStatus       int
+		expectOutputPathsCount int
+		expectOutputPaths      []string
+	}{
+		{
+			scenario:               "missing at least one mandatory file",
+			ctx:                    &api.ContextMock{Context: new(api.Context)},
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "no metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				return ctx
+			}(),
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "invalid metadata form field",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx": "/document.docx",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"foo",
+					},
+				})
+				return ctx
+			}(),
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "no metadata",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"document.docx": "/document.docx",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{}",
+					},
+				})
+				return ctx
+			}(),
+			expectError:            true,
+			expectHttpError:        true,
+			expectHttpStatus:       http.StatusBadRequest,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "error from PDF engine",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return errors.New("foo")
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "cannot add output paths",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
+				ctx.SetCancelled(true)
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
+			expectError:            true,
+			expectHttpError:        false,
+			expectOutputPathsCount: 0,
+		},
+		{
+			scenario: "success",
+			ctx: func() *api.ContextMock {
+				ctx := &api.ContextMock{Context: new(api.Context)}
+				ctx.SetFiles(map[string]string{
+					"file.pdf": "/file.pdf",
+				})
+				ctx.SetValues(map[string][]string{
+					"metadata": {
+						"{\"Creator\": \"foo\", \"Producer\": \"bar\" }",
+					},
+				})
+				return ctx
+			}(),
+			engine: &gotenberg.PdfEngineMock{
+				WriteMetadataMock: func(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+					return nil
+				},
+			},
+			expectError:            false,
+			expectHttpError:        false,
+			expectOutputPathsCount: 1,
+		},
+	} {
+		t.Run(tc.scenario, func(t *testing.T) {
+			tc.ctx.SetLogger(zap.NewNop())
+			c := echo.New().NewContext(nil, nil)
+			c.Set("context", tc.ctx.Context)
+
+			err := writeMetadataRoute(tc.engine).Handler(c)
+
+			if tc.expectError && err == nil {
+				t.Fatal("expected error but got none", err)
+			}
+
+			if !tc.expectError && err != nil {
+				t.Fatalf("expected no error but got: %v", err)
+			}
+
+			var httpErr api.HttpError
+			isHttpError := errors.As(err, &httpErr)
+
+			if tc.expectHttpError && !isHttpError {
+				t.Errorf("expected an HTTP error but got: %v", err)
+			}
+
+			if !tc.expectHttpError && isHttpError {
+				t.Errorf("expected no HTTP error but got one: %v", httpErr)
+			}
+
+			if err != nil && tc.expectHttpError && isHttpError {
+				status, _ := httpErr.HttpError()
+				if status != tc.expectHttpStatus {
+					t.Errorf("expected %d as HTTP status code but got %d", tc.expectHttpStatus, status)
+				}
+			}
+
+			if tc.expectOutputPathsCount != len(tc.ctx.OutputPaths()) {
+				t.Errorf("expected %d output paths but got %d", tc.expectOutputPathsCount, len(tc.ctx.OutputPaths()))
+			}
+
+			for _, path := range tc.expectOutputPaths {
+				if !slices.Contains(tc.ctx.OutputPaths(), path) {
+					t.Errorf("expected '%s' in output paths %v", path, tc.ctx.OutputPaths())
+				}
+			}
+		})
+	}
+}

pkg/modules/pdftk/doc.go

@@ -1,8 +1,10 @@
 // Package pdftk provides an implementation of the gotenberg.PdfEngine
-// interface using the PDFtk command-line tool. This package allows for the
-// merging  of PDF files but does not support conversion to specific PDF
-// formats. The path to the PDFtk binary must be specified using the
-// PDFTK_BIN_PATH environment variable.
+// interface using the PDFtk command-line tool. This package allows for:
+//
+// 1. The merging of PDF files.
+//
+// The path to the PDFtk binary must be specified using the PDFTK_BIN_PATH
+// environment variable.
 //
 // See: https://gitlab.com/pdftk-java/pdftk.
 package pdftk

pkg/modules/pdftk/pdftk.go

@@ -75,6 +75,16 @@ func (engine *PdfTk) Convert(ctx context.Context, logger *zap.Logger, formats go
 	return fmt.Errorf("convert PDF to '%+v' with PDFtk: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// ReadMetadata is not available in this implementation.
+func (engine *PdfTk) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	return nil, fmt.Errorf("read PDF metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// WriteMetadata is not available in this implementation.
+func (engine *PdfTk) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	return fmt.Errorf("write PDF metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*PdfTk)(nil)

pkg/modules/pdftk/pdftk_test.go

@@ -148,3 +148,21 @@ func TestPdfTk_Convert(t *testing.T) {
 		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
 	}
 }
+
+func TestLibreOfficePdfEngine_ReadMetadata(t *testing.T) {
+	engine := new(PdfTk)
+	_, err := engine.ReadMetadata(context.Background(), zap.NewNop(), "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestLibreOfficePdfEngine_WriteMetadata(t *testing.T) {
+	engine := new(PdfTk)
+	err := engine.WriteMetadata(context.Background(), zap.NewNop(), nil, "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}

pkg/modules/qpdf/doc.go

@@ -1,8 +1,10 @@
 // Package qpdf provides an implementation of the gotenberg.PdfEngine
-// interface using the QPDF command-line tool. This package allows for the
-// merging  of PDF files but does not support conversion to specific PDF
-// formats. The path to the QPDF binary must be specified using the
-// QPDK_BIN_PATH environment variable.
+// interface using the QPDF command-line tool. This package allows for:
+//
+// 1. The merging of PDF files.
+//
+// The path to the QPDF binary must be specified using the QPDK_BIN_PATH
+// environment variable.
 //
 // See: https://github.com/qpdf/qpdf.
 package qpdf

pkg/modules/qpdf/qpdf.go

@@ -77,6 +77,16 @@ func (engine *QPdf) Convert(ctx context.Context, logger *zap.Logger, formats got
 	return fmt.Errorf("convert PDF to '%+v' with QPDF: %w", formats, gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// ReadMetadata is not available in this implementation.
+func (engine *QPdf) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPath string) (map[string]interface{}, error) {
+	return nil, fmt.Errorf("read PDF metadata with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
+// WriteMetadata is not available in this implementation.
+func (engine *QPdf) WriteMetadata(ctx context.Context, logger *zap.Logger, metadata map[string]interface{}, inputPath string) error {
+	return fmt.Errorf("write PDF metadata with QPDF: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 var (
 	_ gotenberg.Module      = (*QPdf)(nil)
 	_ gotenberg.Provisioner = (*QPdf)(nil)

pkg/modules/qpdf/qpdf_test.go

@@ -148,3 +148,21 @@ func TestQPdf_Convert(t *testing.T) {
 		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
 	}
 }
+
+func TestLibreOfficePdfEngine_ReadMetadata(t *testing.T) {
+	engine := new(QPdf)
+	_, err := engine.ReadMetadata(context.Background(), zap.NewNop(), "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}
+
+func TestLibreOfficePdfEngine_WriteMetadata(t *testing.T) {
+	engine := new(QPdf)
+	err := engine.WriteMetadata(context.Background(), zap.NewNop(), nil, "")
+
+	if !errors.Is(err, gotenberg.ErrPdfEngineMethodNotSupported) {
+		t.Errorf("expected error %v, but got: %v", gotenberg.ErrPdfEngineMethodNotSupported, err)
+	}
+}

pkg/standard/imports.go

@@ -4,6 +4,7 @@ import (
 	// Standard Gotenberg modules.
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/api"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/chromium"
+	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/exiftool"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/api"
 	_ "github.com/gotenberg/gotenberg/v8/pkg/modules/libreoffice/pdfengine"

test/gotest.sh

@@ -3,4 +3,8 @@
 set -x
 
 go test -race -covermode=atomic -coverprofile=/tests/coverage.txt ./...
-go tool cover -html=coverage.txt -o /tests/coverage.html
+RESULT=$?
+
+go tool cover -html=coverage.txt -o /tests/coverage.html
+
+exit $RESULT