Incremental save not working with Attachment

Question

Saving document with attachment using saveIncremental() method saves document without attachment. Although it does work with save() method i.e attachment are embedded in the document

PDFBox Version - 2.0.26

Code:

 @Test
public static void testAttachment() throws IOException
{
    try (
            InputStream sourceStream = new FileInputStream("src/main/resources/sample_doc_usb_signed_2.pdf");
            final PDDocument document = PDDocument.load(sourceStream);
    )
    {


        List<String> att_list=List.of("src/main/resources/sample_doc.pdf",
                "src/main/resources/sample.docx",
                "src/main/resources/text.jpg"
        );

        final Map<String, PDComplexFileSpecification> embeddedFileMap = new HashMap<>();
        for (String attachPath : att_list) {

            Path path=Path.of(attachPath);
            String mimeType = Files.probeContentType(path);
            long size = Files.size(path);

            File file = new File(attachPath);

            String name = file.getName();

            FileInputStream  attachStream = new FileInputStream(file);

            final PDEmbeddedFile embeddedFile = new PDEmbeddedFile(document, attachStream);
            embeddedFile.setSubtype(mimeType);
            embeddedFile.setSize((int) size);
            embeddedFile.setCreationDate(Calendar.getInstance());
            embeddedFile.setModDate(Calendar.getInstance());
            //TODO - Encoding

            final PDComplexFileSpecification fileSpecification = new PDComplexFileSpecification();
            fileSpecification.setFile(name);
            fileSpecification.setFileDescription("This is attachment for field and supporting");
            fileSpecification.setEmbeddedFile(embeddedFile);


            embeddedFileMap.put(name, fileSpecification);
        }

        final PDEmbeddedFilesNameTreeNode efTree = new PDEmbeddedFilesNameTreeNode();
        efTree.setNames(embeddedFileMap);

        final PDDocumentNameDictionary names = new PDDocumentNameDictionary(document.getDocumentCatalog());
        names.setEmbeddedFiles(efTree);
        document.getDocumentCatalog().setNames(names);

        //This works
        document.save(new FileOutputStream("src/main/resources/sample_wi_attachment.pdf"));

        //Does not work  - File saved without attachments
//            document.saveIncremental(new FileOutputStream("src/main/resources/sample_wi_attachment.pdf"));
        }
    }

Note: Documents used in above test code are simple PDF

Adding attachments to Signed file (File is not certified) invalidates the signature

 private  void addAttachment() throws IOException {

    //File Signed - not Certified
    try(PDDocument document = PDDocument.load(new FileInputStream("src/main/resources/sample-signed_intermediate.pdf"))){
        PDDocumentCatalog catalog = document.getDocumentCatalog();
        PDDocumentNameDictionary names = catalog.getNames();
        PDEmbeddedFilesNameTreeNode efTree = names.getEmbeddedFiles();
        Map<String, PDComplexFileSpecification> embeddedFileMap = efTree.getNames();


        Set<COSDictionary> objectsToWrite = new HashSet<>();

        embeddedFileMap= new HashMap<>();

        List<String> att_list=List.of("src/main/resources/sample_doc.pdf",
                "src/main/resources/AD23884.docx",
                "src/main/resources/text.jpg"

        );

        for (String attachPath : att_list) {

            Path path=Path.of(attachPath);
            String mimeType = Files.probeContentType(path);
            long size = Files.size(path);

            File file = new File(attachPath);

            String name = file.getName();

            FileInputStream  attachStream = new FileInputStream(file);


            final PDEmbeddedFile embeddedFile = new PDEmbeddedFile(document, attachStream);
            embeddedFile.setSubtype(mimeType);
            embeddedFile.setSize((int) size);
            embeddedFile.setCreationDate(Calendar.getInstance());
            embeddedFile.setModDate(Calendar.getInstance());
            //TODO - Encoding

            final PDComplexFileSpecification fileSpecification = new PDComplexFileSpecification();
            fileSpecification.setFile(name);
            fileSpecification.setFileDescription("This is attachment for field and supporting");
            fileSpecification.setEmbeddedFile(embeddedFile);

            embeddedFileMap.put(name, fileSpecification);
        }


        efTree.setNames(embeddedFileMap);

        names.setEmbeddedFiles(efTree);
        document.getDocumentCatalog().setNames(names);

        COSDictionary fieldDictionaryEf =efTree.getCOSObject();
        while (fieldDictionaryEf != null) {
            fieldDictionaryEf.setNeedToBeUpdated(true);
            fieldDictionaryEf = (COSDictionary) fieldDictionaryEf.getDictionaryObject(COSName.PARENT);
        }
        objectsToWrite.add(efTree.getCOSObject());

        COSDictionary fieldDictionaryNam =names.getCOSObject();
        while (fieldDictionaryNam != null) {
            fieldDictionaryNam.setNeedToBeUpdated(true);
            fieldDictionaryNam = (COSDictionary) fieldDictionaryNam.getDictionaryObject(COSName.PARENT);
        }
        objectsToWrite.add(names.getCOSObject());

        COSDictionary fieldDictionary =document.getDocumentCatalog().getCOSObject();
        while (fieldDictionary != null) {
            fieldDictionary.setNeedToBeUpdated(true);
            fieldDictionary = (COSDictionary) fieldDictionary.getDictionaryObject(COSName.PARENT);
        }
        objectsToWrite.add(document.getDocumentCatalog().getCOSObject());

        document.saveIncremental(new FileOutputStream("src/main/resources/attachment.pdf"),objectsToWrite);

    }
    catch (Exception e){
        throw e;
    }
}