Greater protection for pdf files when downloading is disabled

Hi, I  watched a presentation by Raymond Camden that mentioned protecting your PDFs from downloading which I know how to do within the API embed code, He went on to describe a way of protecting the links in the code to the PDF by creating indirect links to the pdf (or something like that ) I will be putting the content on A Joomla Accessd control site so you would need to be registered just to access the pdf, But this would not prevent a determined person from downloading the content.  Could you point me in the direction of a tutorial on protecting your PDFs from downloading but still being accessible to the API? 

Apologies  for the confusing question  I just trying  to better understand what he said and if I could implement  something similar