Signature basic code taken from -> https://www.zetakey.com/codesample-signature.php
PDF display and usage through pdf-lib -> https://pdf-lib.js.org/
PDF with signature - pdf-lib dev way -> Hopding/pdf-lib#418
You can use any pdf file but it must contain a form field prebuilt in it and the id of said field must be "Signature1"
Demo here -> https://paolodigallo.github.io/pdf-lib-signature/