According to this: Any free way to disable copying text in .pdf?
With Adobe Acrobat, you can create passwords to protect pdf files. But others can still use some pdf tools to crack passwords
This to me implies that without cracking the password, you cannot copy any text from a protected document. How does this work from a technical perspective?
Is the text-copy prevention detection simply a feature of Adobe Reader, in which case someone could create a pdf reader that does not enforce this, or is there something more to it?