This might not be a 100% LaTeX question since it is a matter of PDFs, but I think that the LaTeX crowd is the most appropriate audience for it.
I have an unpublished research paper that I am writing in LaTeX, and I have to send its PDF to some people whom I don’t trust completely, so I am paranoid that someone will copy it. I would like to secure it in the sense that the text, table and figures cannot be copied, i.e. that the paper is rendered useless. Both "technical" (e.g. protect pdf) and other (e.g. change irrelevant text in the paper to produce a different version) solutions are seeked.
I know that the safest way is just not to send it around, but I have to, and frankly, I have no clue what to do here. I also know that each PDF can be locked, but that can be easily broken. Putting diagonal watermarks across the whole pages is also not a solution because text and images can be copied, and watermarks destroy the readability. Another thing would be to put watermarks on raster figures directly in the file, so they are useless if copied.
Do you have a solution for this? What did you do in similar situations?