How to change the bookmarks/outlines destination when merge pdf files

[huiyuanai709]

when pdf files merged, the bookmarks/outlines destination's page number tend to update

In PdfBox 3, I can change pdPageDestination's retrievePageNumber code like this

@Test
    void pdfMerge() {
        val mergeUtil = new PDFMergerUtility();
        try(val headerStream = new FileInputStream("/var/header.pdf");
        val bodyStream = new FileInputStream("/var/body.pdf");
        val footerStream = new FileInputStream("/var/footer.pdf");
        val mergeStream = new ByteArrayOutputStream()) {
            mergeUtil.addSource(headerStream);
            mergeUtil.addSource(bodyStream);
            mergeUtil.addSource(footerStream);
            mergeUtil.setDestinationStream(mergeStream);
            mergeUtil.mergeDocuments(MemoryUsageSetting.setupMainMemoryOnly());
            val document = Loader.loadPDF(mergeStream.toByteArray());
            document.getDocumentCatalog().getDocumentOutline().children().forEach(x -> {
                try {
                    val pdPageDestination = document.getDocumentCatalog().findNamedDestinationPage((PDNamedDestination) x.getDestination());
                    pdPageDestination.setPageNumber(pdPageDestination.retrievePageNumber() + 1);
                    x.children().forEach(y -> {
                        PDPageDestination pdPageDestination1 = null;
                        try {
                            pdPageDestination1 = document.getDocumentCatalog().findNamedDestinationPage((PDNamedDestination) y.getDestination());
                            pdPageDestination1.setPageNumber(pdPageDestination1.retrievePageNumber() + 1); // update page number
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    });
                } catch (IOException e) {
                    e.printStackTrace();
                }
            });
            document.save("/var/" + UUIDUtils.generate() + ".pdf");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

but in PdfPig the BookmarkNode is readonly