[Question] Add internal links to PDF attachments

[RichardBray]

I really enjoy using this library, one of the best for PDFs in Javascript out there.

I have a bit of an obscure request. I have created a PDF with attachments but I don't know how to create a link to an attachment in that PDF.

I know it's possible with Acrobat Reader DC and I've actually done it before.

And I know there is a way in pdf-lib to create an internal link to pages, but I don't know how to do it for attachments.

Here is the code I've come up with so far:

// imports omitted

async function main() {
  const pdfDoc = await PDFDocument.create();

  // - Setup PDF buffers
  const page1 = fs.readFileSync("...");
  const page2 = fs.readFileSync("...");
  const page3 = fs.readFileSync("...");

  const page1Doc = await PDFDocument.load(page1);

  // - Attach documents
  await pdfDoc.attach(page2, "page2.pdf", {
    mimeType: "application/pdf",
    description: "Page2",
    creationDate: new Date(),
    modificationDate: new Date(),
  });

  await pdfDoc.attach(page3, "page3.pdf", {
    mimeType: "application/pdf",
    description: "Page3",
    creationDate: new Date(),
    modificationDate: new Date(),
  });

  const [existingPage] = await pdfDoc.copyPages(page1Doc, [0]);
  pdfDoc.addPage(existingPage);

  // - Link to attachment
  const pdfUrlDict = pdfDoc.context.obj({
    Type: "Annot",
    Subtype: "Link",
    Rect: [50, 650, 50 + 100, 650 + 50],
    Border: [0, 0, 2],
    C: [0, 0, 1],
    Dest: [pdfDoc.embeddedFiles[0].ref, "XYZ", null, null, null],
  });
  const pdfUrl = pdfDoc.context.register(pdfUrlDict);
  existingPage.node.set(PDFName.of("Annots"), pdfDoc.context.obj([pdfUrl]));

  // - Save PDF
  const pdfBytes = await pdfDoc.save();
}
main();

The link is visible, it just doesn't open an attachment.

[Hopding]

Hello @RichardBray! Thanks for the well written and concise question 🙂. I'm not sure how to do this offhand, but I would like to support this type of thing with a higher level API. I've added it to the roadmap for tracking: #998.

If you're still interested in this and would like to dig in yourself, you can check section 12.6.4.2 Go-To Actions of the PDF spec.