watermarks that cant be removed?

[vcmota]

I am about to release some class notes to my students and I am looking for a way to watermark/stamp it. Since I have only gave them small parts of my notes in the past, what I have been doing thus far is just write my name and email over each page with pdf editing tools such as xournal. However I am now about to release hundreds of notes, and that is clearly unpractical. There is also the concern that the notes might be easily edited in order to remove the watermark/stamp. My questios are:

[1]Is there a most indicated tool to do that or simply libreoffice (to create a simple text watermark/stamp) + pdftk (to join the watermar/stamp) is the best way to go?
[2]How to make sure the watermark/stamp cannot be removed afterwards?
[3]Are there file formats other than PDF that make removing the watermark/stamp more difficult or even impossible?

Thank you all for your attention.

[Naib]

what are you after? restrict duplication or ensuring the source is known

I always found a bumpmap type "watermark" best as any attempt to remove it isn't a simple colour filter (and thus is a manual effort to remove) but also it take some effort as you can easily erase the information of interest

gimp can do this, imagemajik can and thus you can script it
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[The Doctor]

I think the libreoffice watermark feature will do what you want. Of course, that requires your notes be in a format that libreoffice can open and edit.

Although I find it doubtful that a watermark will discourage students from sharing. You might be better off leaning into it and making a psudo-textbook for anyone interested and host it on your website.
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First things first, but not necessarily in that order.

Apologies if I take a while to respond. I'm currently working on the dematerialization circuit for my blue box.