The main package from the @signpdf family that tries to make signing of PDFs simple in Node.js.

$ npm i -S @signpdf/signpdf node-forge. Then considering you have a well-prepared PDF that already has a signature placeholder and you have prepared a signer implementation usage should be as simple as:

import signpdf from '@signpdf/signpdf';
...
const signedPdf = await signpdf.sign(fs.readFileSync(PATH_TO_PDF_FILE), signer);

If your PDF does not contain a placeholder, we have helpers:

• @signpdf/placeholder-pdfkit010
• @signpdf/placeholder-plain

We also have a single signer implementation currently:

• @signpdf/signer-p12

• The process of signing a document is described in the Digital Signatures in PDF document. As Adobe's files are deprecated, here is the standard as defined by ETSI.
• This lib:
  • requires the signature placeholder to already be in the document (There are helpers included that can try to add it);
  • requires the Contents descriptor in the Sig be placed after the ByteRange one;
  • takes Buffer of the PDF and a Signer implementation to use when signing;
  • does cover only basic scenarios of signing a PDF. If you have suggestions, ideas or anything, please CONTRIBUTE;
• Feel free to copy and paste any part of this code. See its defined Purpose.

To produce PAdES compliant signatures, the ETSI Signature Dictionary SubFilter value must be ETSI.CAdES.detached instead of the standard Adobe value. If you are using placeholder-plain or placeholder-pdfkit010 this can be done with a parameter.

• The whole signing flow is a rework of what's already in pdfsign.js so thanks go to @tbocek