SaaS site Django Python ReactJS

SaaS site with browser based online pdf form filler for comanies.
PDF.js
pdf-lib
jsPDF
pdftk

Features:
-Annotate text, checkmarks & radio buttons
-Signature and initials
-Save
-Fill existing pdf forms
-Attach pdf/image files

Example
pdfdrop.app
https://github.com/PDFdrop/pdfdrop.app

If you already developed similar site - consider that option too!
Experienced developers only