title: How to make files not shareable?
body: <p>I am developing a website with php that is about uploading and selling/buying pdf documents. Of course, I need to program it in a way that makes it impossible (or at least very hard) to copy the purchased documents.</p>
  
  <p>Do you know of any mechanism to do this? Is it a programming issue or rather a pdf issue? Also, are there maybe other file types that you recommend that are better for this purpose than pdf? Maybe there should be another solution than downloading the pdf files but rather only viewing them in a browser?</p>
  
  <p>Thank you!
  Charles</p>
  
  <p>EDIT</p>
  
  <p>Maybe some more information is needed: The users on the website will upload the pdfs themselves, so there is no way to create the pdfs only when they are downloaded, as they are purely user generated input.</p>