Anyone who is good at this who might want to write up a quick guide?

[Anonyma'am]

I don't even know what this is.

Well, hidden watermarks or identifying information about the owner. Opening a book in calibre makes it quite easy to search for identifying information such as store number, order number and things like that. My question is if anybody has experience in editing books and/ or has got a routine for it, What to look for and so on. Thing is, it takes a lot of work doing this and some tips on how to do this quicker would be welcome.