This is much newer, but I think it will eventually be included.

This tool is an implementation of https://pastebin.com/raw/E1xgCUmb

Thanks. I found the background article from Torrent Freak useful.

https://torrentfreak.com/researchers-crack-social-drm-ebook-...

Thanks for that. The reading was a bit thick on the polemics, but I also found it an easy to read and understand overview of ebook watermark functionality for someone like me who's unfamiliar with the field.