Apache PDFBox - Adobe Acrobat prompts saving

Question

I'm using Apache PDFBox version 2.0.16 to add paging to an existing PDF file. My method is working great, the generated PDF is fine. However, when I open the file with Adobe Acrobat Reader, if I try to close the file, it prompts an alert asking me if I want to save the file even though I haven't edited anything, and the file is not editable at first. I can't manage to understand what's happening, and how to prevent it from prompting saving

My code is the following:

private void paging(ByteArrayOutputStream os) throws IOException {
    PDDocument doc = PDDocument.load(new ByteArrayInputStream(os.toByteArray()));
    PDFont font = getFont(doc);
    PDPageTree pages = doc.getDocumentCatalog().getPages();
    for (int i = 0; i < pages.getCount(); i++) {
        PDPage page = pages.get(i);
        PDPageContentStream contentStream = new PDPageContentStream(doc, page, PDPageContentStream.AppendMode.APPEND, true, false);
        contentStream.beginText();
        contentStream.setFont(font, FONT_SIZE);
        contentStream.setNonStrokingColor(Color.BLACK);
        contentStream.newLineAtOffset(page.getCropBox().getWidth() - 40,  15);
        contentStream.showText((i + 1) + " / " + pages.getCount());
        contentStream.endText();
        contentStream.close();
    }

    doc.save(os);
    doc.close();
}

Answer 1

reset 'os' before saving, so that your ByteArrayOutputStream gets cleared and positioned at the beginning.

os.reset();

Also call load() directly with the byte array:

PDDocument.load(os.toByteArray());

and update to the current version, which is 2.0.19 at this time.