feat: add embeds metadata

.bruno/Chromium/Convert/HTML to PDF.bru

@@ -11,7 +11,7 @@ post {
 }
 
 body:multipart-form {
-  files: @file(../../test/integration/testdata/page-1-html/index.html)
+  files: @file(../test/integration/testdata/page-1-html/index.html)
   ~landscape: false
   ~printBackground: false
   ~scale: 1.0
@@ -50,6 +50,9 @@ body:multipart-form {
   ~metadata: {"Author":"Bruno","Title":"Test"}
   ~userPassword:
   ~ownerPassword:
+  ~embeds: @file(../test/integration/testdata/embed_1.xml)
+  ~embeds: @file(../test/integration/testdata/embed_2.xml)
+  ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/Chromium/Convert/Markdown to PDF.bru

@@ -51,6 +51,9 @@ body:multipart-form {
   ~metadata: {"Author":"Bruno","Title":"Test"}
   ~userPassword:
   ~ownerPassword:
+  ~embeds: @file(../test/integration/testdata/embed_1.xml)
+  ~embeds: @file(../test/integration/testdata/embed_2.xml)
+  ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/Chromium/Convert/URL to PDF.bru

@@ -50,6 +50,9 @@ body:multipart-form {
   ~metadata: {"Author":"Bruno","Title":"Test"}
   ~userPassword:
   ~ownerPassword:
+  ~embeds: @file(../test/integration/testdata/embed_1.xml)
+  ~embeds: @file(../test/integration/testdata/embed_2.xml)
+  ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/LibreOffice/Convert to PDF.bru

@@ -11,7 +11,7 @@ post {
 }
 
 body:multipart-form {
-  files: @file(../../test/integration/testdata/page_1.docx)
+  files: @file(../test/integration/testdata/page_1.docx)
   ~password:
   ~landscape: false
   ~nativePageRanges:
@@ -67,6 +67,9 @@ body:multipart-form {
   ~metadata: {"Author":"Bruno","Title":"Test"}
   ~userPassword:
   ~ownerPassword:
+  ~embeds: @file(../test/integration/testdata/embed_1.xml)
+  ~embeds: @file(../test/integration/testdata/embed_2.xml)
+  ~embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
   ~watermarkSource: text
   ~watermarkExpression: CONFIDENTIAL
   ~watermarkPages:

.bruno/PDF Engines/Embed/Embed Files.bru

@@ -11,8 +11,10 @@ post {
 }
 
 body:multipart-form {
-  files: @file(../../test/integration/testdata/page_1.pdf)
+  files: @file(../test/integration/testdata/page_1.pdf)
-  embeds: @file(../../test/integration/testdata/page_1.pdf)
+  embeds: @file(../test/integration/testdata/embed_1.xml)
+  embeds: @file(../test/integration/testdata/embed_2.xml)
+  embedsMetadata: {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"}, "embed_2.xml":{"mimeType":"text/xml","relationship":"Data"}}
   ~downloadFrom: [{"url":"https://example.com/attachment.xml","embedded":true}]
 }
 

Makefile

@@ -76,7 +76,8 @@ PDFENGINES_WATERMARK_ENGINES=pdfcpu,pdftk
 PDFENGINES_STAMP_ENGINES=pdfcpu,pdftk
 PDFENGINES_ENCRYPT_ENGINES=qpdf,pdfcpu,pdftk
 PDFENGINES_ROTATE_ENGINES=pdfcpu,pdftk
-PDFENGINES_EMBED_ENGINES=pdfcpu
+PDFENGINES_EMBED_ENGINES=qpdf,pdfcpu
+PDFENGINES_EMBED_METADATA_ENGINES=qpdf
 PROMETHEUS_NAMESPACE=gotenberg
 PROMETHEUS_COLLECT_INTERVAL=1s
 PROMETHEUS_DISABLE_ROUTE_TELEMETRY=true

compose.yaml

@@ -77,6 +77,7 @@ services:
       - "--pdfengines-encrypt-engines=${PDFENGINES_ENCRYPT_ENGINES}"
       - "--pdfengines-rotate-engines=${PDFENGINES_ROTATE_ENGINES}"
       - "--pdfengines-embed-engines=${PDFENGINES_EMBED_ENGINES}"
+      - "--pdfengines-embed-metadata-engines=${PDFENGINES_EMBED_METADATA_ENGINES}"
       - "--pdfengines-disable-routes=${PDFENGINES_DISABLE_ROUTES}"
       - "--prometheus-namespace=${PROMETHEUS_NAMESPACE}"
       - "--prometheus-collect-interval=${PROMETHEUS_COLLECT_INTERVAL}"

pkg/gotenberg/mocks.go

@@ -45,20 +45,21 @@ func (mod *DebuggableMock) Debug() map[string]any {
 //
 //nolint:dupl
 type PdfEngineMock struct {
-	MergeMock          func(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error
+	MergeMock              func(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error
-	SplitMock          func(ctx context.Context, logger *slog.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
+	SplitMock              func(ctx context.Context, logger *slog.Logger, mode SplitMode, inputPath, outputDirPath string) ([]string, error)
-	FlattenMock        func(ctx context.Context, logger *slog.Logger, inputPath string) error
+	FlattenMock            func(ctx context.Context, logger *slog.Logger, inputPath string) error
-	ConvertMock        func(ctx context.Context, logger *slog.Logger, formats PdfFormats, inputPath, outputPath string) error
+	ConvertMock            func(ctx context.Context, logger *slog.Logger, formats PdfFormats, inputPath, outputPath string) error
-	ReadMetadataMock   func(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error)
+	ReadMetadataMock       func(ctx context.Context, logger *slog.Logger, inputPath string) (map[string]any, error)
-	PageCountMock      func(ctx context.Context, logger *slog.Logger, inputPath string) (int, error)
+	PageCountMock          func(ctx context.Context, logger *slog.Logger, inputPath string) (int, error)
-	WriteMetadataMock  func(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error
+	WriteMetadataMock      func(ctx context.Context, logger *slog.Logger, metadata map[string]any, inputPath string) error
-	ReadBookmarksMock  func(ctx context.Context, logger *slog.Logger, inputPath string) ([]Bookmark, error)
+	ReadBookmarksMock      func(ctx context.Context, logger *slog.Logger, inputPath string) ([]Bookmark, error)
-	EncryptMock        func(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error
+	EncryptMock            func(ctx context.Context, logger *slog.Logger, inputPath, userPassword, ownerPassword string) error
-	EmbedFilesMock     func(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error
+	EmbedFilesMock         func(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error
-	WriteBookmarksMock func(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error
+	EmbedFilesMetadataMock func(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error
-	WatermarkMock      func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
+	WriteBookmarksMock     func(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error
-	StampMock          func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
+	WatermarkMock          func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
-	RotateMock         func(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
+	StampMock              func(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
+	RotateMock             func(ctx context.Context, logger *slog.Logger, inputPath string, angle int, pages string) error
 }
 
 func (engine *PdfEngineMock) Merge(ctx context.Context, logger *slog.Logger, inputPaths []string, outputPath string) error {
@@ -101,6 +102,10 @@ func (engine *PdfEngineMock) EmbedFiles(ctx context.Context, logger *slog.Logger
 	return engine.EmbedFilesMock(ctx, logger, filePaths, inputPath)
 }
 
+func (engine *PdfEngineMock) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	return engine.EmbedFilesMetadataMock(ctx, logger, metadata, inputPath)
+}
+
 func (engine *PdfEngineMock) WriteBookmarks(ctx context.Context, logger *slog.Logger, inputPath string, bookmarks []Bookmark) error {
 	return engine.WriteBookmarksMock(ctx, logger, inputPath, bookmarks)
 }

pkg/gotenberg/pdfengine.go

@@ -201,6 +201,12 @@ type PdfEngine interface {
 	// TODO: attachments instead? Rename the route?
 	EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error
 
+	// EmbedFilesMetadata sets metadata (such as MIME type and AFRelationship)
+	// on already-embedded files in a PDF. The metadata map is keyed by
+	// filename, with each value being a map of property names to values
+	// (e.g., "mimeType" and "relationship").
+	EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error
+
 	// Watermark applies a watermark (behind page content) to a PDF file.
 	Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp Stamp) error
 

pkg/modules/api/formdata.go

@@ -1,6 +1,7 @@
 package api
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
 	"math"
@@ -391,6 +392,38 @@ func (form *FormData) Embeds(target *[]string) *FormData {
 	return form
 }
 
+// EmbedsMetadata parses the "embedsMetadata" form field (a JSON string) into
+// a map keyed by filename. Each value is a map of property names to values
+// (e.g., "mimeType" and "relationship").
+//
+//	var metadata map[string]map[string]string
+//
+//	ctx.FormData().EmbedsMetadata(&metadata)
+func (form *FormData) EmbedsMetadata(target *map[string]map[string]string) *FormData {
+	if form.errors != nil {
+		return form
+	}
+
+	val, ok := form.values["embedsMetadata"]
+	if !ok || len(val) == 0 || val[0] == "" {
+		return form
+	}
+
+	raw := val[0]
+	parsed := make(map[string]map[string]string)
+
+	err := json.Unmarshal([]byte(raw), &parsed)
+	if err != nil {
+		form.append(
+			fmt.Errorf("form field 'embedsMetadata' is invalid: %w", err),
+		)
+		return form
+	}
+
+	*target = parsed
+	return form
+}
+
 // MandatoryPaths binds the absolute paths of form data files, according to a
 // list of file extensions, to a string slice variable. It populates an error
 // if there is no file for given file extensions.

pkg/modules/chromium/routes.go

@@ -421,6 +421,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stamp := pdfengines.FormDataPdfStamp(form, false)
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
+			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
 
 			var url string
 			err := form.
@@ -437,7 +438,7 @@ func convertUrlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 				stamp.Expression = stampFile
 			}
 
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert URL to PDF: %w", err)
 			}
@@ -496,6 +497,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stamp := pdfengines.FormDataPdfStamp(form, false)
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
+			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
 
 			var inputPath string
 			err := form.
@@ -514,7 +516,7 @@ func convertHtmlRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 
 			url := fmt.Sprintf("file://%s", inputPath)
 			options.AllowedFilePrefixes = []string{ctx.DirPath()}
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert HTML to PDF: %w", err)
 			}
@@ -575,6 +577,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			stamp := pdfengines.FormDataPdfStamp(form, false)
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			rotateAngle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
+			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
 
 			var (
 				inputPath     string
@@ -602,7 +605,7 @@ func convertMarkdownRoute(chromium Api, engine gotenberg.PdfEngine) api.Route {
 			}
 
 			options.AllowedFilePrefixes = []string{ctx.DirPath()}
-			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, watermark, stamp, rotateAngle, rotatePages)
+			err = convertUrl(ctx, chromium, engine, url, options, mode, pdfFormats, metadata, userPassword, ownerPassword, embedPaths, embedsMetadata, watermark, stamp, rotateAngle, rotatePages)
 			if err != nil {
 				return fmt.Errorf("convert markdown to PDF: %w", err)
 			}
@@ -727,7 +730,7 @@ 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, options PdfOptions, mode gotenberg.SplitMode, pdfFormats gotenberg.PdfFormats, metadata map[string]any, userPassword, ownerPassword string, embedPaths []string, watermark, stamp gotenberg.Stamp, rotateAngle int, rotatePages string) error {
+func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url string, options PdfOptions, mode gotenberg.SplitMode, pdfFormats gotenberg.PdfFormats, metadata map[string]any, userPassword, ownerPassword string, embedPaths []string, embedsMetadata map[string]map[string]string, watermark, stamp gotenberg.Stamp, rotateAngle int, rotatePages string) error {
 	outputPath := ctx.GeneratePath(".pdf")
 	// See https://github.com/gotenberg/gotenberg/issues/1130.
 	filename := ctx.OutputFilename(outputPath)
@@ -831,6 +834,11 @@ func convertUrl(ctx *api.Context, chromium Api, engine gotenberg.PdfEngine, url
 		return fmt.Errorf("embed files into PDFs: %w", err)
 	}
 
+	err = pdfengines.EmbedFilesMetadataStub(ctx, engine, embedsMetadata, convertOutputPaths)
+	if err != nil {
+		return fmt.Errorf("set embeds metadata: %w", err)
+	}
+
 	err = pdfengines.EncryptPdfStub(ctx, engine, userPassword, ownerPassword, convertOutputPaths)
 	if err != nil {
 		return fmt.Errorf("encrypt PDFs: %w", err)

pkg/modules/exiftool/exiftool.go

@@ -531,6 +531,11 @@ func (engine *ExifTool) Rotate(ctx context.Context, logger *slog.Logger, inputPa
 	return err
 }
 
+// EmbedFilesMetadata is not available in this implementation.
+func (engine *ExifTool) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	return fmt.Errorf("set embeds metadata with ExifTool: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*ExifTool)(nil)

pkg/modules/libreoffice/pdfengine/pdfengine.go

@@ -115,6 +115,11 @@ func (engine *LibreOfficePdfEngine) EmbedFiles(ctx context.Context, logger *slog
 	return fmt.Errorf("embed files with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
 }
 
+// EmbedFilesMetadata is not available in this implementation.
+func (engine *LibreOfficePdfEngine) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	return fmt.Errorf("set embeds metadata with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Watermark is not available in this implementation.
 func (engine *LibreOfficePdfEngine) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	return fmt.Errorf("watermark PDF with LibreOffice: %w", gotenberg.ErrPdfEngineMethodNotSupported)

pkg/modules/libreoffice/routes.go

@@ -37,6 +37,7 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 			stamp := pdfengines.FormDataPdfStamp(form, false)
 			stampFile := pdfengines.FormDataPdfStampFile(form)
 			angle, rotatePages := pdfengines.FormDataPdfRotate(form, false)
+			embedsMetadata := pdfengines.FormDataPdfEmbedsMetadata(form)
 
 			zeroValuedSplitMode := gotenberg.SplitMode{}
 
@@ -495,6 +496,11 @@ func convertRoute(libreOffice libreofficeapi.Uno, engine gotenberg.PdfEngine) ap
 				return fmt.Errorf("embed files into PDFs: %w", err)
 			}
 
+			err = pdfengines.EmbedFilesMetadataStub(ctx, engine, embedsMetadata, outputPaths)
+			if err != nil {
+				return fmt.Errorf("set embeds metadata: %w", err)
+			}
+
 			err = pdfengines.EncryptPdfStub(ctx, engine, userPassword, ownerPassword, outputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)

pkg/modules/pdfcpu/pdfcpu.go

@@ -447,6 +447,11 @@ func (engine *PdfCpu) WriteBookmarks(ctx context.Context, logger *slog.Logger, i
 	return nil
 }
 
+// EmbedFilesMetadata is not available in this implementation.
+func (engine *PdfCpu) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	return fmt.Errorf("set embeds metadata with pdfcpu: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // EmbedFiles embeds files into a PDF. All files are embedded as file attachments
 // without modifying the main PDF content.
 func (engine *PdfCpu) EmbedFiles(ctx context.Context, logger *slog.Logger, filePaths []string, inputPath string) error {

pkg/modules/pdfengines/multi.go

@@ -22,6 +22,7 @@ type multiPdfEngines struct {
 	writeMetadataEngines  []gotenberg.PdfEngine
 	passwordEngines       []gotenberg.PdfEngine
 	embedEngines          []gotenberg.PdfEngine
+	embedMetadataEngines  []gotenberg.PdfEngine
 	readBookmarksEngines  []gotenberg.PdfEngine
 	writeBookmarksEngines []gotenberg.PdfEngine
 	watermarkEngines      []gotenberg.PdfEngine
@@ -38,6 +39,7 @@ func newMultiPdfEngines(
 	writeMetadataEngines,
 	passwordEngines,
 	embedEngines,
+	embedMetadataEngines,
 	readBookmarksEngines,
 	writeBookmarksEngines,
 	watermarkEngines,
@@ -53,6 +55,7 @@ func newMultiPdfEngines(
 		writeMetadataEngines:  writeMetadataEngines,
 		passwordEngines:       passwordEngines,
 		embedEngines:          embedEngines,
+		embedMetadataEngines:  embedMetadataEngines,
 		readBookmarksEngines:  readBookmarksEngines,
 		writeBookmarksEngines: writeBookmarksEngines,
 		watermarkEngines:      watermarkEngines,
@@ -603,6 +606,43 @@ func (multi *multiPdfEngines) Rotate(ctx context.Context, logger *slog.Logger, i
 	return err
 }
 
+// EmbedFilesMetadata sets metadata on embedded files using the first available
+// engine that supports it.
+//
+//nolint:dupl
+func (multi *multiPdfEngines) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	tracer := gotenberg.Tracer()
+	ctx, span := tracer.Start(ctx, "pdfengines.EmbedFilesMetadata", trace.WithSpanKind(trace.SpanKindInternal))
+	defer span.End()
+
+	var err error
+	errChan := make(chan error, 1)
+
+	for _, engine := range multi.embedMetadataEngines {
+		go func(engine gotenberg.PdfEngine) {
+			errChan <- engine.EmbedFilesMetadata(ctx, logger, metadata, inputPath)
+		}(engine)
+
+		select {
+		case setErr := <-errChan:
+			if setErr != nil {
+				err = errors.Join(err, setErr)
+			} else {
+				span.SetStatus(codes.Ok, "")
+				return nil
+			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+
+	err = fmt.Errorf("set embeds metadata using multi PDF engines: %w", err)
+	span.RecordError(err)
+	span.SetStatus(codes.Error, err.Error())
+
+	return err
+}
+
 // Interface guards.
 var (
 	_ gotenberg.PdfEngine = (*multiPdfEngines)(nil)

pkg/modules/pdfengines/pdfengines.go

@@ -36,6 +36,7 @@ type PdfEngines struct {
 	writeMetadataNames  []string
 	encryptNames        []string
 	embedNames          []string
+	embedMetadataNames  []string
 	readBookmarksNames  []string
 	writeBookmarksNames []string
 	watermarkNames      []string
@@ -59,6 +60,7 @@ func (mod *PdfEngines) Descriptor() gotenberg.ModuleDescriptor {
 			fs.StringSlice("pdfengines-write-metadata-engines", []string{"exiftool"}, "Set the PDF engines and their order for the write metadata feature - empty means all")
 			fs.StringSlice("pdfengines-encrypt-engines", []string{"qpdf", "pdftk", "pdfcpu"}, "Set the PDF engines and their order for the password protection feature - empty means all")
 			fs.StringSlice("pdfengines-embed-engines", []string{"pdfcpu"}, "Set the PDF engines and their order for the file embedding feature - empty means all")
+			fs.StringSlice("pdfengines-embed-metadata-engines", []string{"qpdf"}, "Set the PDF engines and their order for the embed metadata feature - empty means all")
 			fs.StringSlice("pdfengines-read-bookmarks-engines", []string{"pdfcpu"}, "Set the PDF engines and their order for the read bookmarks feature - empty means all")
 			fs.StringSlice("pdfengines-write-bookmarks-engines", []string{"pdfcpu"}, "Set the PDF engines and their order for the write bookmarks feature - empty means all")
 			fs.StringSlice("pdfengines-watermark-engines", []string{"pdfcpu", "pdftk"}, "Set the PDF engines and their order for the watermark feature - empty means all")
@@ -91,6 +93,7 @@ func (mod *PdfEngines) Provision(ctx *gotenberg.Context) error {
 	writeMetadataNames := flags.MustStringSlice("pdfengines-write-metadata-engines")
 	encryptNames := flags.MustStringSlice("pdfengines-encrypt-engines")
 	embedNames := flags.MustStringSlice("pdfengines-embed-engines")
+	embedMetadataNames := flags.MustStringSlice("pdfengines-embed-metadata-engines")
 	readBookmarksNames := flags.MustStringSlice("pdfengines-read-bookmarks-engines")
 	writeBookmarksNames := flags.MustStringSlice("pdfengines-write-bookmarks-engines")
 	watermarkNames := flags.MustStringSlice("pdfengines-watermark-engines")
@@ -162,6 +165,11 @@ func (mod *PdfEngines) Provision(ctx *gotenberg.Context) error {
 		mod.embedNames = embedNames
 	}
 
+	mod.embedMetadataNames = defaultNames
+	if len(embedMetadataNames) > 0 {
+		mod.embedMetadataNames = embedMetadataNames
+	}
+
 	mod.readBookmarksNames = defaultNames
 	if len(readBookmarksNames) > 0 {
 		mod.readBookmarksNames = readBookmarksNames
@@ -236,6 +244,7 @@ func (mod *PdfEngines) Validate() error {
 	findNonExistingEngines(mod.writeMetadataNames)
 	findNonExistingEngines(mod.encryptNames)
 	findNonExistingEngines(mod.embedNames)
+	findNonExistingEngines(mod.embedMetadataNames)
 	findNonExistingEngines(mod.readBookmarksNames)
 	findNonExistingEngines(mod.writeBookmarksNames)
 	findNonExistingEngines(mod.watermarkNames)
@@ -261,6 +270,7 @@ func (mod *PdfEngines) SystemMessages() []string {
 		fmt.Sprintf("write metadata engines - %s", strings.Join(mod.writeMetadataNames, " ")),
 		fmt.Sprintf("encrypt engines - %s", strings.Join(mod.encryptNames, " ")),
 		fmt.Sprintf("embed engines - %s", strings.Join(mod.embedNames, " ")),
+		fmt.Sprintf("embed metadata engines - %s", strings.Join(mod.embedMetadataNames, " ")),
 		fmt.Sprintf("read bookmarks engines - %s", strings.Join(mod.readBookmarksNames, " ")),
 		fmt.Sprintf("write bookmarks engines - %s", strings.Join(mod.writeBookmarksNames, " ")),
 		fmt.Sprintf("watermark engines - %s", strings.Join(mod.watermarkNames, " ")),
@@ -294,6 +304,7 @@ func (mod *PdfEngines) PdfEngine() (gotenberg.PdfEngine, error) {
 		engines(mod.writeMetadataNames),
 		engines(mod.encryptNames),
 		engines(mod.embedNames),
+		engines(mod.embedMetadataNames),
 		engines(mod.readBookmarksNames),
 		engines(mod.writeBookmarksNames),
 		engines(mod.watermarkNames),

pkg/modules/pdfengines/routes.go

@@ -443,6 +443,30 @@ func FormDataPdfEmbeds(form *api.FormData) []string {
 	return embedPaths
 }
 
+// FormDataPdfEmbedsMetadata extracts embeds metadata from form data.
+// The "embedsMetadata" field is a JSON string keyed by filename.
+func FormDataPdfEmbedsMetadata(form *api.FormData) map[string]map[string]string {
+	var metadata map[string]map[string]string
+	form.EmbedsMetadata(&metadata)
+	return metadata
+}
+
+// EmbedFilesMetadataStub sets metadata on embedded files in PDFs.
+func EmbedFilesMetadataStub(ctx *api.Context, engine gotenberg.PdfEngine, metadata map[string]map[string]string, inputPaths []string) error {
+	if len(metadata) == 0 {
+		return nil
+	}
+
+	for _, inputPath := range inputPaths {
+		err := engine.EmbedFilesMetadata(ctx, ctx.Log(), metadata, inputPath)
+		if err != nil {
+			return fmt.Errorf("set embeds metadata on PDF '%s': %w", inputPath, err)
+		}
+	}
+
+	return nil
+}
+
 // FormDataPdfEncrypt extracts encryption parameters from form data.
 func FormDataPdfEncrypt(form *api.FormData) (userPassword, ownerPassword string) {
 	form.String("userPassword", &userPassword, "")
@@ -638,6 +662,7 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 			stamp := FormDataPdfStamp(form, false)
 			stampFile := FormDataPdfStampFile(form)
 			angle, rotatePages := FormDataPdfRotate(form, false)
+			embedsMetadata := FormDataPdfEmbedsMetadata(form)
 
 			var inputPaths []string
 			var flatten bool
@@ -754,6 +779,11 @@ func mergeRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("embed files into PDFs: %w", err)
 			}
 
+			err = EmbedFilesMetadataStub(ctx, engine, embedsMetadata, outputPaths)
+			if err != nil {
+				return fmt.Errorf("set embeds metadata: %w", err)
+			}
+
 			err = EncryptPdfStub(ctx, engine, userPassword, ownerPassword, outputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)
@@ -789,6 +819,7 @@ func splitRoute(engine gotenberg.PdfEngine) api.Route {
 			stamp := FormDataPdfStamp(form, false)
 			stampFile := FormDataPdfStampFile(form)
 			angle, rotatePages := FormDataPdfRotate(form, false)
+			embedsMetadata := FormDataPdfEmbedsMetadata(form)
 
 			var inputPaths []string
 			var flatten bool
@@ -856,6 +887,11 @@ func splitRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("embed files into PDFs: %w", err)
 			}
 
+			err = EmbedFilesMetadataStub(ctx, engine, embedsMetadata, convertOutputPaths)
+			if err != nil {
+				return fmt.Errorf("set embeds metadata: %w", err)
+			}
+
 			err = EncryptPdfStub(ctx, engine, userPassword, ownerPassword, convertOutputPaths)
 			if err != nil {
 				return fmt.Errorf("encrypt PDFs: %w", err)
@@ -1180,6 +1216,7 @@ func embedRoute(engine gotenberg.PdfEngine) api.Route {
 
 			form := ctx.FormData()
 			embedPaths := FormDataPdfEmbeds(form)
+			embedsMetadata := FormDataPdfEmbedsMetadata(form)
 
 			var inputPaths []string
 			err := form.
@@ -1193,6 +1230,11 @@ func embedRoute(engine gotenberg.PdfEngine) api.Route {
 				return fmt.Errorf("embed files into PDFs: %w", err)
 			}
 
+			err = EmbedFilesMetadataStub(ctx, engine, embedsMetadata, inputPaths)
+			if err != nil {
+				return fmt.Errorf("set embeds metadata: %w", err)
+			}
+
 			err = ctx.AddOutputPaths(inputPaths...)
 			if err != nil {
 				return fmt.Errorf("add output paths: %w", err)

pkg/modules/pdftk/pdftk.go

@@ -495,6 +495,11 @@ func (engine *PdfTk) Rotate(ctx context.Context, logger *slog.Logger, inputPath
 	return nil
 }
 
+// EmbedFilesMetadata is not available in this implementation.
+func (engine *PdfTk) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	return fmt.Errorf("set embeds metadata with PDFtk: %w", gotenberg.ErrPdfEngineMethodNotSupported)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.Module      = (*PdfTk)(nil)

pkg/modules/qpdf/qpdf.go

@@ -3,12 +3,14 @@ package qpdf
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"log/slog"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"syscall"
 
 	"go.opentelemetry.io/otel/codes"
@@ -348,6 +350,291 @@ func (engine *QPdf) EmbedFiles(ctx context.Context, logger *slog.Logger, filePat
 	return err
 }
 
+// EmbedFilesMetadata sets metadata on already-embedded files in a PDF using
+// QPDF's JSON manipulation. It sets /AFRelationship on Filespec objects,
+// /Subtype on EmbeddedFile streams, and ensures the Catalog /AF array
+// references the Filespec objects.
+func (engine *QPdf) EmbedFilesMetadata(ctx context.Context, logger *slog.Logger, metadata map[string]map[string]string, inputPath string) error {
+	ctx, span := gotenberg.Tracer().Start(ctx, "qpdf.EmbedFilesMetadata",
+		trace.WithSpanKind(trace.SpanKindClient),
+		trace.WithAttributes(semconv.ServerAddress(engine.binPath)),
+	)
+	defer span.End()
+
+	if len(metadata) == 0 {
+		span.SetStatus(codes.Ok, "")
+		return nil
+	}
+
+	logger.DebugContext(ctx, fmt.Sprintf("setting embeds metadata on %s with QPDF", inputPath))
+
+	args := append([]string{inputPath}, engine.globalArgs...)
+	args = append(args, "--newline-before-endstream", "--json-output")
+
+	output, err := engine.execCaptureOutput(ctx, args...)
+	if err != nil {
+		err = fmt.Errorf("get PDF JSON with QPDF: %w", err)
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	objects, err := parsePdfObjects(output)
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	catalogRef, catalogValue, filespecRefs, updateObjects := patchFilespecMetadata(logger, objects, metadata)
+	if len(filespecRefs) == 0 {
+		span.SetStatus(codes.Ok, "")
+		return nil
+	}
+
+	patchCatalogAF(catalogRef, catalogValue, filespecRefs, updateObjects)
+
+	err = engine.writeAndApplyUpdate(ctx, logger, inputPath, updateObjects)
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+		return err
+	}
+
+	span.SetStatus(codes.Ok, "")
+	return nil
+}
+
+// execCaptureOutput runs QPDF and returns its stdout. This uses
+// exec.CommandContext directly because gotenberg.Cmd does not support
+// capturing stdout (it only pipes to debug logs).
+func (engine *QPdf) execCaptureOutput(ctx context.Context, args ...string) ([]byte, error) {
+	cmd := exec.CommandContext(ctx, engine.binPath, args...) //nolint:gosec
+	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
+	return cmd.Output()
+}
+
+// parsePdfObjects parses QPDF JSON v2 output and returns the objects map.
+func parsePdfObjects(output []byte) (map[string]json.RawMessage, error) {
+	var pdfJSON struct {
+		Qpdf []json.RawMessage `json:"qpdf"`
+	}
+	if err := json.Unmarshal(output, &pdfJSON); err != nil {
+		return nil, fmt.Errorf("parse PDF JSON: %w", err)
+	}
+	if len(pdfJSON.Qpdf) < 2 {
+		return nil, fmt.Errorf("unexpected QPDF JSON structure: expected at least 2 elements")
+	}
+
+	var objects map[string]json.RawMessage
+	if err := json.Unmarshal(pdfJSON.Qpdf[1], &objects); err != nil {
+		return nil, fmt.Errorf("parse QPDF objects: %w", err)
+	}
+
+	return objects, nil
+}
+
+// patchFilespecMetadata walks QPDF objects to find Filespecs matching the
+// metadata keys. It sets /AFRelationship and /Subtype on matching objects
+// and returns the catalog reference, catalog value, filespec references,
+// and the update objects map.
+func patchFilespecMetadata(logger *slog.Logger, objects map[string]json.RawMessage, metadata map[string]map[string]string) (string, map[string]any, []string, map[string]any) {
+	updateObjects := make(map[string]any)
+	var catalogRef string
+	var catalogValue map[string]any
+	var filespecRefs []string
+
+	for ref, raw := range objects {
+		var obj map[string]json.RawMessage
+		if err := json.Unmarshal(raw, &obj); err != nil {
+			continue
+		}
+
+		valueRaw, hasValue := obj["value"]
+		if !hasValue {
+			continue
+		}
+
+		var value map[string]any
+		if err := json.Unmarshal(valueRaw, &value); err != nil {
+			continue
+		}
+
+		typeVal, _ := value["/Type"].(string)
+
+		if typeVal == "/Catalog" {
+			catalogRef = ref
+			catalogValue = value
+		}
+
+		if typeVal == "/Filespec" {
+			uf, _ := value["/UF"].(string)
+			if uf == "" {
+				uf, _ = value["/F"].(string)
+			}
+
+			cleanUf := stripQpdfStringPrefix(uf)
+
+			meta, exists := metadata[cleanUf]
+			if !exists {
+				continue
+			}
+
+			if rel, ok := meta["relationship"]; ok {
+				value["/AFRelationship"] = "/" + rel
+			}
+
+			if mimeType, ok := meta["mimeType"]; ok {
+				if ef, ok := value["/EF"].(map[string]any); ok {
+					efRef, _ := ef["/F"].(string)
+					if efRef != "" {
+						setStreamSubtype(logger, objects, updateObjects, efRef, mimeType)
+					}
+				}
+			}
+
+			filespecRefs = append(filespecRefs, ref)
+			updateObjects[ref] = map[string]any{"value": value}
+		}
+	}
+
+	return catalogRef, catalogValue, filespecRefs, updateObjects
+}
+
+// patchCatalogAF ensures the Catalog /AF array references all filespec objects.
+func patchCatalogAF(catalogRef string, catalogValue map[string]any, filespecRefs []string, updateObjects map[string]any) {
+	if catalogRef == "" || catalogValue == nil {
+		return
+	}
+
+	afSet := make(map[string]bool)
+	existingAF, _ := catalogValue["/AF"].([]any)
+	for _, r := range existingAF {
+		if s, ok := r.(string); ok {
+			afSet[s] = true
+		}
+	}
+	for _, ref := range filespecRefs {
+		// Object references in values use "9 0 R" format,
+		// not the "obj:9 0 R" key format.
+		valRef := strings.TrimPrefix(ref, "obj:")
+		if !afSet[valRef] {
+			existingAF = append(existingAF, valRef)
+		}
+	}
+	catalogValue["/AF"] = existingAF
+	updateObjects[catalogRef] = map[string]any{"value": catalogValue}
+}
+
+// writeAndApplyUpdate marshals the update objects as QPDF JSON v2, writes
+// them to a temp file, and applies the update via --update-from-json.
+func (engine *QPdf) writeAndApplyUpdate(ctx context.Context, logger *slog.Logger, inputPath string, updateObjects map[string]any) error {
+	updateJSON := map[string]any{
+		"qpdf": []any{
+			map[string]any{
+				"jsonversion":                  2,
+				"pushedinheritedpageresources": false,
+				"calledgetallpages":            false,
+				"maxobjectid":                  0,
+			},
+			updateObjects,
+		},
+	}
+
+	jsonBytes, err := json.Marshal(updateJSON)
+	if err != nil {
+		return fmt.Errorf("marshal update JSON: %w", err)
+	}
+
+	tmpFile, err := os.CreateTemp(filepath.Dir(inputPath), "qpdf-embeds-metadata-*.json")
+	if err != nil {
+		return fmt.Errorf("create temp file for update JSON: %w", err)
+	}
+	defer os.Remove(tmpFile.Name())
+
+	if _, err := tmpFile.Write(jsonBytes); err != nil {
+		tmpFile.Close()
+		return fmt.Errorf("write update JSON: %w", err)
+	}
+	if err := tmpFile.Close(); err != nil {
+		return fmt.Errorf("close temp file: %w", err)
+	}
+
+	updateArgs := make([]string, 0, 5+len(engine.globalArgs))
+	updateArgs = append(updateArgs, inputPath)
+	updateArgs = append(updateArgs, engine.globalArgs...)
+	updateArgs = append(updateArgs, "--newline-before-endstream")
+	updateArgs = append(updateArgs, "--update-from-json="+tmpFile.Name())
+	updateArgs = append(updateArgs, "--replace-input")
+
+	cmd, err := gotenberg.CommandContext(ctx, logger, engine.binPath, updateArgs...)
+	if err != nil {
+		return fmt.Errorf("create command for JSON update: %w", err)
+	}
+
+	_, err = cmd.Exec()
+	if err != nil {
+		return fmt.Errorf("update embeds metadata with QPDF: %w", err)
+	}
+
+	return nil
+}
+
+// setStreamSubtype finds a stream object by reference and sets the /Subtype
+// key in its dict.
+func setStreamSubtype(logger *slog.Logger, objects map[string]json.RawMessage, updateObjects map[string]any, ref, mimeType string) {
+	objKey := ref
+	if !strings.HasPrefix(objKey, "obj:") {
+		objKey = "obj:" + objKey
+	}
+	raw, ok := objects[objKey]
+	if !ok {
+		logger.Warn(fmt.Sprintf("set stream subtype on %s: object not found", ref))
+		return
+	}
+
+	var obj map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &obj); err != nil {
+		logger.Warn(fmt.Sprintf("set stream subtype on %s: unmarshal object: %s", ref, err))
+		return
+	}
+
+	streamRaw, ok := obj["stream"]
+	if !ok {
+		logger.Warn(fmt.Sprintf("set stream subtype on %s: no stream key", ref))
+		return
+	}
+
+	var stream map[string]any
+	if err := json.Unmarshal(streamRaw, &stream); err != nil {
+		logger.Warn(fmt.Sprintf("set stream subtype on %s: unmarshal stream: %s", ref, err))
+		return
+	}
+
+	dict, ok := stream["dict"].(map[string]any)
+	if !ok {
+		logger.Warn(fmt.Sprintf("set stream subtype on %s: stream dict is not a map", ref))
+		return
+	}
+
+	// QPDF JSON uses literal name syntax; it handles PDF name
+	// encoding internally when writing the binary PDF.
+	dict["/Subtype"] = "/" + mimeType
+	stream["dict"] = dict
+	updateObjects[objKey] = map[string]any{"stream": stream}
+}
+
+// stripQpdfStringPrefix removes the type prefix that QPDF adds to JSON
+// string values. Known prefixes: "u:" (Unicode), "b:" (binary), "e:" (encoded).
+func stripQpdfStringPrefix(s string) string {
+	for _, prefix := range []string{"u:", "b:", "e:"} {
+		if strings.HasPrefix(s, prefix) {
+			return s[len(prefix):]
+		}
+	}
+	return s
+}
+
 // Watermark is not available in this implementation.
 func (engine *QPdf) Watermark(ctx context.Context, logger *slog.Logger, inputPath string, stamp gotenberg.Stamp) error {
 	_, span := gotenberg.Tracer().Start(ctx, "qpdf.Watermark",

pkg/modules/qpdf/qpdf_test.go

@@ -0,0 +1,271 @@
+package qpdf
+
+import (
+	"encoding/json"
+	"log/slog"
+	"os"
+	"testing"
+)
+
+func TestStripQpdfStringPrefix(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{"unicode prefix", "u:factur-x.xml", "factur-x.xml"},
+		{"binary prefix", "b:binary.bin", "binary.bin"},
+		{"encoded prefix", "e:encoded.txt", "encoded.txt"},
+		{"no prefix", "plain.xml", "plain.xml"},
+		{"empty string", "", ""},
+		{"prefix only", "u:", ""},
+		{"colon in value", "u:file:name.xml", "file:name.xml"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := stripQpdfStringPrefix(tt.input)
+			if got != tt.expected {
+				t.Errorf("stripQpdfStringPrefix(%q) = %q, want %q", tt.input, got, tt.expected)
+			}
+		})
+	}
+}
+
+func TestParsePdfObjects(t *testing.T) {
+	tests := []struct {
+		name      string
+		input     string
+		wantKeys  []string
+		wantError bool
+	}{
+		{
+			name:     "valid QPDF JSON v2",
+			input:    `{"qpdf":[{"jsonversion":2},{"obj:1 0 R":{"value":{"/Type":"/Catalog"}}}]}`,
+			wantKeys: []string{"obj:1 0 R"},
+		},
+		{
+			name:      "invalid JSON",
+			input:     `not json`,
+			wantError: true,
+		},
+		{
+			name:      "empty qpdf array",
+			input:     `{"qpdf":[]}`,
+			wantError: true,
+		},
+		{
+			name:      "only header element",
+			input:     `{"qpdf":[{"jsonversion":2}]}`,
+			wantError: true,
+		},
+		{
+			name:     "multiple objects",
+			input:    `{"qpdf":[{},{"obj:1 0 R":{"value":{}},"obj:2 0 R":{"value":{}}}]}`,
+			wantKeys: []string{"obj:1 0 R", "obj:2 0 R"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			objects, err := parsePdfObjects([]byte(tt.input))
+			if tt.wantError {
+				if err == nil {
+					t.Error("expected error, got nil")
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+			for _, key := range tt.wantKeys {
+				if _, ok := objects[key]; !ok {
+					t.Errorf("expected key %q in objects", key)
+				}
+			}
+		})
+	}
+}
+
+func TestPatchFilespecMetadata(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
+
+	t.Run("sets AFRelationship on matching Filespec", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:1 0 R": json.RawMessage(`{"value":{"/Type":"/Catalog"}}`),
+			"obj:2 0 R": json.RawMessage(`{"value":{"/Type":"/Filespec","/UF":"u:factur-x.xml"}}`),
+		}
+		metadata := map[string]map[string]string{
+			"factur-x.xml": {"relationship": "Data"},
+		}
+
+		catalogRef, _, filespecRefs, updateObjects := patchFilespecMetadata(logger, objects, metadata)
+
+		if catalogRef != "obj:1 0 R" {
+			t.Errorf("catalogRef = %q, want %q", catalogRef, "obj:1 0 R")
+		}
+		if len(filespecRefs) != 1 || filespecRefs[0] != "obj:2 0 R" {
+			t.Errorf("filespecRefs = %v, want [obj:2 0 R]", filespecRefs)
+		}
+		updated, ok := updateObjects["obj:2 0 R"]
+		if !ok {
+			t.Fatal("expected obj:2 0 R in updateObjects")
+		}
+		value := updated.(map[string]any)["value"].(map[string]any)
+		if value["/AFRelationship"] != "/Data" {
+			t.Errorf("/AFRelationship = %v, want /Data", value["/AFRelationship"])
+		}
+	})
+
+	t.Run("skips Filespec with no matching metadata", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:1 0 R": json.RawMessage(`{"value":{"/Type":"/Filespec","/UF":"u:other.xml"}}`),
+		}
+		metadata := map[string]map[string]string{
+			"factur-x.xml": {"relationship": "Data"},
+		}
+
+		_, _, filespecRefs, _ := patchFilespecMetadata(logger, objects, metadata)
+		if len(filespecRefs) != 0 {
+			t.Errorf("filespecRefs = %v, want empty", filespecRefs)
+		}
+	})
+
+	t.Run("falls back to /F when /UF is absent", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:1 0 R": json.RawMessage(`{"value":{"/Type":"/Filespec","/F":"u:factur-x.xml"}}`),
+		}
+		metadata := map[string]map[string]string{
+			"factur-x.xml": {"relationship": "Alternative"},
+		}
+
+		_, _, filespecRefs, updateObjects := patchFilespecMetadata(logger, objects, metadata)
+		if len(filespecRefs) != 1 {
+			t.Fatalf("filespecRefs = %v, want 1 entry", filespecRefs)
+		}
+		value := updateObjects["obj:1 0 R"].(map[string]any)["value"].(map[string]any)
+		if value["/AFRelationship"] != "/Alternative" {
+			t.Errorf("/AFRelationship = %v, want /Alternative", value["/AFRelationship"])
+		}
+	})
+
+	t.Run("sets stream Subtype via EF reference", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:2 0 R": json.RawMessage(`{"value":{"/Type":"/Filespec","/UF":"u:factur-x.xml","/EF":{"/F":"3 0 R"}}}`),
+			"obj:3 0 R": json.RawMessage(`{"stream":{"dict":{"/Type":"/EmbeddedFile"}}}`),
+		}
+		metadata := map[string]map[string]string{
+			"factur-x.xml": {"mimeType": "text/xml"},
+		}
+
+		_, _, _, updateObjects := patchFilespecMetadata(logger, objects, metadata)
+		streamObj, ok := updateObjects["obj:3 0 R"]
+		if !ok {
+			t.Fatal("expected obj:3 0 R in updateObjects")
+		}
+		stream := streamObj.(map[string]any)["stream"].(map[string]any)
+		dict := stream["dict"].(map[string]any)
+		if dict["/Subtype"] != "/text/xml" {
+			t.Errorf("/Subtype = %v, want /text/xml", dict["/Subtype"])
+		}
+	})
+}
+
+func TestPatchCatalogAF(t *testing.T) {
+	t.Run("adds filespec refs to AF array", func(t *testing.T) {
+		catalogValue := map[string]any{"/Type": "/Catalog"}
+		updateObjects := make(map[string]any)
+
+		patchCatalogAF("obj:1 0 R", catalogValue, []string{"obj:2 0 R", "obj:3 0 R"}, updateObjects)
+
+		af, ok := catalogValue["/AF"].([]any)
+		if !ok {
+			t.Fatal("expected /AF to be []any")
+		}
+		if len(af) != 2 {
+			t.Fatalf("/AF has %d entries, want 2", len(af))
+		}
+		if af[0] != "2 0 R" || af[1] != "3 0 R" {
+			t.Errorf("/AF = %v, want [2 0 R, 3 0 R]", af)
+		}
+	})
+
+	t.Run("does not duplicate existing refs", func(t *testing.T) {
+		catalogValue := map[string]any{
+			"/Type": "/Catalog",
+			"/AF":   []any{"2 0 R"},
+		}
+		updateObjects := make(map[string]any)
+
+		patchCatalogAF("obj:1 0 R", catalogValue, []string{"obj:2 0 R", "obj:3 0 R"}, updateObjects)
+
+		af := catalogValue["/AF"].([]any)
+		if len(af) != 2 {
+			t.Fatalf("/AF has %d entries, want 2", len(af))
+		}
+	})
+
+	t.Run("no-op when catalogRef is empty", func(t *testing.T) {
+		updateObjects := make(map[string]any)
+		patchCatalogAF("", nil, []string{"obj:2 0 R"}, updateObjects)
+		if len(updateObjects) != 0 {
+			t.Error("expected no updates for empty catalogRef")
+		}
+	})
+}
+
+func TestSetStreamSubtype(t *testing.T) {
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelError}))
+
+	t.Run("sets Subtype in stream dict", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:3 0 R": json.RawMessage(`{"stream":{"dict":{"/Type":"/EmbeddedFile"}}}`),
+		}
+		updateObjects := make(map[string]any)
+
+		setStreamSubtype(logger, objects, updateObjects, "obj:3 0 R", "text/xml")
+
+		streamObj := updateObjects["obj:3 0 R"].(map[string]any)["stream"].(map[string]any)
+		dict := streamObj["dict"].(map[string]any)
+		if dict["/Subtype"] != "/text/xml" {
+			t.Errorf("/Subtype = %v, want /text/xml", dict["/Subtype"])
+		}
+	})
+
+	t.Run("auto-adds obj: prefix to ref", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:5 0 R": json.RawMessage(`{"stream":{"dict":{}}}`),
+		}
+		updateObjects := make(map[string]any)
+
+		setStreamSubtype(logger, objects, updateObjects, "5 0 R", "application/pdf")
+
+		if _, ok := updateObjects["obj:5 0 R"]; !ok {
+			t.Error("expected obj:5 0 R in updateObjects")
+		}
+	})
+
+	t.Run("warns on missing object", func(t *testing.T) {
+		objects := map[string]json.RawMessage{}
+		updateObjects := make(map[string]any)
+
+		setStreamSubtype(logger, objects, updateObjects, "obj:99 0 R", "text/xml")
+
+		if len(updateObjects) != 0 {
+			t.Error("expected no updates for missing object")
+		}
+	})
+
+	t.Run("warns on object without stream key", func(t *testing.T) {
+		objects := map[string]json.RawMessage{
+			"obj:3 0 R": json.RawMessage(`{"value":{"/Type":"/Page"}}`),
+		}
+		updateObjects := make(map[string]any)
+
+		setStreamSubtype(logger, objects, updateObjects, "obj:3 0 R", "text/xml")
+
+		if len(updateObjects) != 0 {
+			t.Error("expected no updates for non-stream object")
+		}
+	})
+}

test/integration/features/pdfengines_embed.feature

@@ -17,6 +17,21 @@ Feature: /forms/pdfengines/embed
     Then the response PDF(s) should have the "embed_1.xml" file embedded
     Then the response PDF(s) should have the "embed_2.xml" file embedded
 
+  Scenario: POST /forms/pdfengines/embed with metadata
+    Given I have a default Gotenberg container
+    When I make a "POST" request to Gotenberg at the "/forms/pdfengines/embed" endpoint with the following form data and header(s):
+      | files          | testdata/page_1.pdf                                                                                                              | file  |
+      | embeds         | testdata/embed_1.xml                                                                                                             | file  |
+      | embeds         | testdata/embed_2.xml                                                                                                             | file  |
+      | embedsMetadata | {"embed_1.xml":{"mimeType":"text/xml","relationship":"Data"},"embed_2.xml":{"mimeType":"text/xml","relationship":"Alternative"}} | field |
+    Then the response status code should be 200
+    And the response header "Content-Type" should be "application/pdf"
+    And there should be 1 PDF(s) in the response
+    And the response PDF(s) should have the "embed_1.xml" file embedded
+    And the response PDF(s) should have the "embed_1.xml" file embedded with relationship "Data"
+    And the response PDF(s) should have the "embed_2.xml" file embedded
+    And the response PDF(s) should have the "embed_2.xml" file embedded with relationship "Alternative"
+
   @download-from
   Scenario: POST /forms/pdfengines/embed with (Download From)
     Given I have a default Gotenberg container

test/integration/scenario/containers.go

@@ -9,6 +9,7 @@ import (
 
 	"github.com/moby/moby/api/types/container"
 	"github.com/testcontainers/testcontainers-go"
+	"github.com/testcontainers/testcontainers-go/exec"
 	"github.com/testcontainers/testcontainers-go/network"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
@@ -138,7 +139,7 @@ func execCommandInIntegrationToolsContainer(ctx context.Context, cmd []string, p
 		}
 	}(c, ctx)
 
-	_, output, err := c.Exec(ctx, cmd)
+	_, output, err := c.Exec(ctx, cmd, exec.Multiplexed())
 	if err != nil {
 		return "", fmt.Errorf("exec %q: %w", cmd, err)
 	}

test/integration/scenario/scenario.go

@@ -1262,6 +1262,68 @@ func (s *scenario) thePdfsShouldHaveEmbeddedFile(ctx context.Context, kind, shou
 	return nil
 }
 
+func (s *scenario) thePdfsShouldHaveEmbeddedFileWithRelationship(ctx context.Context, kind, embed, relationship string) error {
+	dirPath := s.teststoreDir
+
+	_, err := os.Stat(dirPath)
+	if os.IsNotExist(err) {
+		return fmt.Errorf("directory %q does not exist", dirPath)
+	}
+
+	var paths []string
+	err = filepath.Walk(dirPath, func(path string, info os.FileInfo, pathErr error) error {
+		if pathErr != nil {
+			return pathErr
+		}
+		if strings.EqualFold(filepath.Ext(info.Name()), ".pdf") {
+			paths = append(paths, path)
+		}
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("walk %q: %w", dirPath, err)
+	}
+
+	for _, path := range paths {
+		cmd := []string{
+			"verapdf",
+			"--off",
+			"--loglevel",
+			"0",
+			"--extract",
+			"embeddedFile",
+			filepath.Base(path),
+		}
+
+		output, err := execCommandInIntegrationToolsContainer(ctx, cmd, path)
+		if err != nil {
+			return fmt.Errorf("exec %q: %w", cmd, err)
+		}
+
+		fileNameTag := fmt.Sprintf("<fileName>%s</fileName>", embed)
+		relationshipTag := fmt.Sprintf("<afRelationship>%s</afRelationship>", relationship)
+
+		blocks := strings.Split(output, "</embeddedFile>")
+		found := false
+		for _, block := range blocks {
+			if !strings.Contains(block, fileNameTag) {
+				continue
+			}
+			if !strings.Contains(block, relationshipTag) {
+				return fmt.Errorf("embedded file %q missing afRelationship %q", embed, relationship)
+			}
+			found = true
+			break
+		}
+
+		if !found {
+			return fmt.Errorf("embedded file %q not found in verapdf output", embed)
+		}
+	}
+
+	return nil
+}
+
 func InitializeScenario(ctx *godog.ScenarioContext) {
 	s := &scenario{}
 	ctx.Before(func(ctx context.Context, sc *godog.Scenario) (context.Context, error) {
@@ -1300,6 +1362,7 @@ func InitializeScenario(ctx *godog.ScenarioContext) {
 	ctx.Then(`^the (response|webhook request) PDF\(s\) (should|should NOT) be flatten$`, s.thePdfsShouldBeFlatten)
 	ctx.Then(`^the (response|webhook request) PDF\(s\) (should|should NOT) be encrypted`, s.thePdfsShouldBeEncrypted)
 	ctx.Then(`^the (response|webhook request) PDF\(s\) (should|should NOT) have the "([^"]*)" file embedded$`, s.thePdfsShouldHaveEmbeddedFile)
+	ctx.Then(`^the (response|webhook request) PDF\(s\) should have the "([^"]*)" file embedded with relationship "([^"]*)"$`, s.thePdfsShouldHaveEmbeddedFileWithRelationship)
 	ctx.Then(`^the "([^"]*)" PDF should have (\d+) page\(s\)$`, s.thePdfShouldHavePages)
 	ctx.Then(`^the "([^"]*)" PDF (should|should NOT) be set to landscape orientation$`, s.thePdfShouldBeSetToLandscapeOrientation)
 	ctx.Then(`^the "([^"]*)" PDF (should|should NOT) have the following content at page (\d+):$`, s.thePdfShouldHaveTheFollowingContentAtPage)