To be fair, if you wanted to stop copying of text it would be easiest just to drop the ToUnicode mapping against the fonts and then itβs a manual process for people to recreate them.
That also breaks search (and more importantly screen reader accessibility), and if you're professionally required to specifically produce PDFs with these security features enabled, you're pretty likely to be working in a context where that would be illegal.
You could do it (and Adobe has with some documents AFAIK) by using some kind of DRM solution, limiting access to approved software. That software wouldn't then be allowed to expose its UI tree to accessibility APIs, except for approved screen readers that embed a particular key in their executables. Those approved screen readers would have restrictions around what they can do with the text. Sure, everything can be broken, for example with third-party fake speech synthesizers or speech recognition applied to the screen reader's output (as contemporary OSes don't even provide good DRM mechanisms for audio), but it would make the process that much harder.
