Preventing PDFs from being downloaded

[greener]

I am just learning PHP - which by the way rocks - and I'm trying to finalize some security issues on my site: www.cougarnotes.com. The idea is that users log in to the site and based on their access rights (which are stored in a mysql database) they can view/print pdf documents containing lecture notes. I have everything working so that only logged on users with the right access can get to the pdf files, but I want users to ONLY BE ABLE TO PRINT the pdfs or VIEW THEM ONLINE, not download the documents. Is there a way to do this?

[gizmola]

No, there's no way to do that because the pdf's are being rendered by the user's local computer.  This raises the age old question of: can you show people information without having them see it?  When you think on the conundrum, I"m sure you'll realize that this isn't possible --- you can't give someone a snack and not allow them to eat it, or for that matter to save a piece for their friend. 

 

You can, using certain libraries, generate pdf's on the fly that you password protect.  This adds an extra barrier to the pdf and makes it that much harder for someone to distribute to the masses.  If you *really* want to do this, there's a way, but what you're asking for is pretty much copy protection, and every form of copy protection ever invented to date has been broken.

[PHP Monkeh]

Even doing that, there's still nothing stopping someone using print screen, and then they can even create their own PDF from those screens.  I work at a University and I know that we have a lot of copyright issues with our eBooks.  As far as I know our software detects how much they copy/paste from the PDF, and I don't think they can save it either - except this is a custom browser plug in rather than through PHP.