diff --git a/backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java b/backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java
index b7d50f99..f53a60b3 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/service/DocumentService.java
@@ -350,6 +350,52 @@ public class DocumentService {
         return documentRepository.save(doc);
     }
 
+    /**
+     * Applies a bulk-edit DTO to a single document atomically.
+     * Tags and receivers are additive (merged into existing sets); sender and the
+     * three location fields are replace-on-non-blank (null/blank means "no change").
+     * Wrapped in its own transaction so a failure on one document never partially
+     * mutates another in the batch loop.
+     */
+    @Transactional
+    public Document applyBulkEditToDocument(UUID id, org.raddatz.familienarchiv.dto.DocumentBulkEditDTO dto) {
+        Document doc = documentRepository.findById(id)
+                .orElseThrow(() -> DomainException.notFound(ErrorCode.DOCUMENT_NOT_FOUND, "Document not found: " + id));
+
+        if (dto.getTagNames() != null && !dto.getTagNames().isEmpty()) {
+            Set<Tag> merged = new HashSet<>(doc.getTags());
+            for (String name : dto.getTagNames()) {
+                String clean = name.trim();
+                if (!clean.isEmpty()) {
+                    merged.add(tagService.findOrCreate(clean));
+                }
+            }
+            doc.setTags(merged);
+        }
+
+        if (dto.getSenderId() != null) {
+            doc.setSender(personService.getById(dto.getSenderId()));
+        }
+
+        if (dto.getReceiverIds() != null && !dto.getReceiverIds().isEmpty()) {
+            Set<Person> merged = new HashSet<>(doc.getReceivers());
+            merged.addAll(personService.getAllById(dto.getReceiverIds()));
+            doc.setReceivers(merged);
+        }
+
+        if (StringUtils.hasText(dto.getDocumentLocation())) {
+            doc.setDocumentLocation(dto.getDocumentLocation());
+        }
+        if (StringUtils.hasText(dto.getArchiveBox())) {
+            doc.setArchiveBox(dto.getArchiveBox());
+        }
+        if (StringUtils.hasText(dto.getArchiveFolder())) {
+            doc.setArchiveFolder(dto.getArchiveFolder());
+        }
+
+        return documentRepository.save(doc);
+    }
+
     /**
      * Hilfsmethode: Erstellt Platzhalter (wird später vom Excel-Service genutzt)
      */
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java
index 4c34862b..3065391c 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/service/DocumentServiceTest.java
@@ -1917,4 +1917,198 @@ class DocumentServiceTest {
                 .isInstanceOf(DomainException.class)
                 .hasMessageContaining("titles");
     }
+
+    // ─── applyBulkEditToDocument ─────────────────────────────────────────────
+
+    private static org.raddatz.familienarchiv.dto.DocumentBulkEditDTO bulkDto() {
+        return new org.raddatz.familienarchiv.dto.DocumentBulkEditDTO();
+    }
+
+    @Test
+    void applyBulkEditToDocument_throwsNotFound_whenDocumentMissing() {
+        UUID id = UUID.randomUUID();
+        when(documentRepository.findById(id)).thenReturn(Optional.empty());
+
+        assertThatThrownBy(() -> documentService.applyBulkEditToDocument(id, bulkDto()))
+                .isInstanceOf(DomainException.class)
+                .hasMessageContaining(id.toString());
+    }
+
+    @Test
+    void applyBulkEditToDocument_appliesTagsAdditively_preservesExistingTags() {
+        UUID id = UUID.randomUUID();
+        Tag existing = Tag.builder().id(UUID.randomUUID()).name("Brief").build();
+        Tag added = Tag.builder().id(UUID.randomUUID()).name("Kurrent").build();
+        Document doc = Document.builder().id(id).title("T")
+                .tags(new HashSet<>(Set.of(existing)))
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+        when(tagService.findOrCreate("Kurrent")).thenReturn(added);
+
+        var dto = bulkDto();
+        dto.setTagNames(List.of("Kurrent"));
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getTags()).containsExactlyInAnyOrder(existing, added);
+    }
+
+    @Test
+    void applyBulkEditToDocument_skipsTags_whenTagNamesIsNull() {
+        UUID id = UUID.randomUUID();
+        Tag existing = Tag.builder().id(UUID.randomUUID()).name("Brief").build();
+        Document doc = Document.builder().id(id).title("T")
+                .tags(new HashSet<>(Set.of(existing)))
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        documentService.applyBulkEditToDocument(id, bulkDto());
+
+        assertThat(doc.getTags()).containsExactly(existing);
+        verify(tagService, never()).findOrCreate(any());
+    }
+
+    @Test
+    void applyBulkEditToDocument_skipsTags_whenTagNamesIsEmpty() {
+        UUID id = UUID.randomUUID();
+        Tag existing = Tag.builder().id(UUID.randomUUID()).name("Brief").build();
+        Document doc = Document.builder().id(id).title("T")
+                .tags(new HashSet<>(Set.of(existing)))
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        var dto = bulkDto();
+        dto.setTagNames(List.of());
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getTags()).containsExactly(existing);
+        verify(tagService, never()).findOrCreate(any());
+    }
+
+    @Test
+    void applyBulkEditToDocument_replacesSender_whenSenderIdProvided() {
+        UUID id = UUID.randomUUID();
+        UUID senderId = UUID.randomUUID();
+        Person oldSender = Person.builder().id(UUID.randomUUID()).firstName("Old").build();
+        Person newSender = Person.builder().id(senderId).firstName("New").build();
+        Document doc = Document.builder().id(id).title("T")
+                .sender(oldSender)
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+        when(personService.getById(senderId)).thenReturn(newSender);
+
+        var dto = bulkDto();
+        dto.setSenderId(senderId);
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getSender()).isEqualTo(newSender);
+    }
+
+    @Test
+    void applyBulkEditToDocument_skipsSender_whenSenderIdIsNull() {
+        UUID id = UUID.randomUUID();
+        Person existing = Person.builder().id(UUID.randomUUID()).firstName("X").build();
+        Document doc = Document.builder().id(id).title("T")
+                .sender(existing)
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        documentService.applyBulkEditToDocument(id, bulkDto());
+
+        assertThat(doc.getSender()).isEqualTo(existing);
+        verify(personService, never()).getById(any());
+    }
+
+    @Test
+    void applyBulkEditToDocument_addsReceiversAdditively_preservesExistingReceivers() {
+        UUID id = UUID.randomUUID();
+        UUID newReceiverId = UUID.randomUUID();
+        Person existing = Person.builder().id(UUID.randomUUID()).firstName("Old").build();
+        Person added = Person.builder().id(newReceiverId).firstName("New").build();
+        Document doc = Document.builder().id(id).title("T")
+                .receivers(new HashSet<>(Set.of(existing)))
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+        when(personService.getAllById(List.of(newReceiverId))).thenReturn(List.of(added));
+
+        var dto = bulkDto();
+        dto.setReceiverIds(List.of(newReceiverId));
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getReceivers()).containsExactlyInAnyOrder(existing, added);
+    }
+
+    @Test
+    void applyBulkEditToDocument_skipsReceivers_whenReceiverIdsIsNullOrEmpty() {
+        UUID id = UUID.randomUUID();
+        Person existing = Person.builder().id(UUID.randomUUID()).firstName("Old").build();
+        Document doc = Document.builder().id(id).title("T")
+                .receivers(new HashSet<>(Set.of(existing)))
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        var dto = bulkDto();
+        dto.setReceiverIds(List.of());
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getReceivers()).containsExactly(existing);
+        verify(personService, never()).getAllById(any());
+    }
+
+    @Test
+    void applyBulkEditToDocument_replacesArchiveBoxAndFolderAndDocumentLocation_whenProvided() {
+        UUID id = UUID.randomUUID();
+        Document doc = Document.builder().id(id).title("T")
+                .archiveBox("OldBox")
+                .archiveFolder("OldFolder")
+                .documentLocation("OldLocation")
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        var dto = bulkDto();
+        dto.setArchiveBox("NewBox");
+        dto.setArchiveFolder("NewFolder");
+        dto.setDocumentLocation("NewLocation");
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getArchiveBox()).isEqualTo("NewBox");
+        assertThat(doc.getArchiveFolder()).isEqualTo("NewFolder");
+        assertThat(doc.getDocumentLocation()).isEqualTo("NewLocation");
+    }
+
+    @Test
+    void applyBulkEditToDocument_skipsLocationFields_whenBlankOrNull() {
+        UUID id = UUID.randomUUID();
+        Document doc = Document.builder().id(id).title("T")
+                .archiveBox("KeepBox")
+                .archiveFolder("KeepFolder")
+                .documentLocation("KeepLocation")
+                .receivers(new HashSet<>())
+                .build();
+        when(documentRepository.findById(id)).thenReturn(Optional.of(doc));
+        when(documentRepository.save(any())).thenAnswer(inv -> inv.getArgument(0));
+
+        var dto = bulkDto();
+        dto.setArchiveBox("   ");
+        dto.setArchiveFolder("");
+        // documentLocation left null
+        documentService.applyBulkEditToDocument(id, dto);
+
+        assertThat(doc.getArchiveBox()).isEqualTo("KeepBox");
+        assertThat(doc.getArchiveFolder()).isEqualTo("KeepFolder");
+        assertThat(doc.getDocumentLocation()).isEqualTo("KeepLocation");
+    }
 }