pdftool.py is a new tool I developed. This version has only one command: iu (incremental updates).
With this command, one can check if a PDF has incremental updates, and then select different versions of this PDF with incremental updates.
A PDF with incremental updates, is a PDF that has been modified by appending changes to the document at the end of the PDF file, without modifying the original content.
Here is a video explaining incremental updates and the use of my tool.
I reference 2 blog posts in the video: “Solving a Little PDF Puzzle” and “Shoulder Surfing a Malicious PDF Author“.
pdftool_V0_0_1.zip (https)
MD5: ED2BBE886008C737CC06E22F4F0FE8A1
SHA256: 401E88FBFAEC4382A50FE59430D04FE6111F9911958AB09BA7530C26043FDA87
Didier Stevens 
Amazing! Thanks for implementing the project I’ve been slowly working toward, while learning about PDFs; I’m sure your code will be helpful when I get stuck or am looking for inspiration about how to do more/better.
Comment by Alex — Sunday 31 January 2021 @ 20:28
Correction for your first sentence: you write “one command: ui” instead of “iu”.
(Feel free to delete this comment; it doesn’t contribute anything technical.)
Comment by Alex — Sunday 31 January 2021 @ 20:34
Thanks!
Comment by Didier Stevens — Sunday 31 January 2021 @ 20:57