fix(pdgengines): encrypt behavior accross different engines

pkg/modules/pdfengines/routes.go

@@ -270,6 +270,16 @@ func EncryptPdfStub(ctx *api.Context, engine gotenberg.PdfEngine, userPassword,
 	for _, inputPath := range inputPaths {
 		err := engine.Encrypt(ctx, ctx.Log(), inputPath, userPassword, ownerPassword)
 		if err != nil {
+			if errors.Is(err, gotenberg.ErrPdfEngineEncryptionPasswordsNotSupported) {
+				return api.WrapError(
+					err,
+					api.NewSentinelHttpError(
+						http.StatusBadRequest,
+						"Invalid form data: both 'userPassword' and 'ownerPassword' form fields must be provided and different",
+					),
+				)
+			}
+
 			return fmt.Errorf("encrypt PDF '%s': %w", inputPath, err)
 		}
 	}