I have pdf's on a clients site using tags, the client has requested that I prevent users from right clicking the document to stop them from saving the files (Yes I am aware this is foolish but they are adamant that this is what they want).
I have looked at many ways of achieving this but none seem to work (Some work put prevent scrolling).
I would also like to disable CRTL+S.
While, as you said the approach is foolish and there are so many ways around it, for most users, you can just capture the contextmenu event and use event.preventDefault() to stop the context menu from appearing (or provide a custom one). It's supported by all major desktop browsers, so should do what you need it to do without hindering scrolling or anything else.
For Ctrl+S, I've not attempted this before, but filtering the keydown event may be an option (though tbh I doubt it). Other than that, I don't know of any other way to do this.