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add Digital Signature to pdf with pdfKit and react-signature-canvas for NodeJS / GraphQL

to create hand-craft signature with signaturePad, add date and save to a pdf. then add signature PDF as an additional page attach to the main pdf.

** need remove alpha from image in order for pdfKit to create pdf by: 
1. set background color to whte

canvasProps={{ className: classes.sigPad }}

2. to image/jpeg
const imageData = sigPad.current

3. merge pdfs using
export const mergePdfs = async (pdf1: string, pdf2: string, pdf: string) => {
return new Promise((resolve, reject) => {
merge([pdf1, pdf2], pdf, (error: any) => {
if (error) {
return reject(error)

Here are other ways to sign PDF:

Node Library:

import signer from 'node-signpdf';
const signedPdf = signer.sign(


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