How to protect watermarks in PDF from being deleted?

I am negotiating with publishers to publish my textbook. Often publishers ask to send the full version of the book before signing a contract. I have already had the opportunity to make sure from personal experience that all publishers in Russia are cheating, so I am trying to protect my PDF file with the text of the book by adding a watermark on all pages using the background package. However, the watermark that this package and others like it makes can be removed in Adobe Acrobat. Passwords also do not help, as there are programs on the Internet that remove password in PDF files. Is there a way to protect the watermark from being deleted?

Here is one version of invisible watermark I used:

usepackage[
    placement=top
    ,vshift=-8.7em
    ,contents={copyright И.А. Котельников, копия для Infra-M today}
    %,color=gray,opacity=0.1
    ,color=white
    ,scale=1.3
]{background}

This code produces white strung invisible on white page, but the text can be found using standard Find menu.