I run a small publishing company and we want to provide exam copies of our books to professors. At present our exam copies have the words EXAM COPY as a water mark on every page and we've also made the files so that they can't be printed or easily copied. However, we'd like to also restrict these PDFs so that they can only be opened 5 times. I've read about FileOpen but that approach seems a bit more complex than needed. Is there any other way to restrict the number of times that a PDF file can be opened once it is downloaded? Thanks in advance for any suggestions.
DRM soltions like FileOpen are your best bet for PDFs. Others include Adobe's LiveCycle Rights Managment, LockLizard, Armjisoft PDF Security OwnerGuard, etc.
They all work and are priced differently, but there's really nothing for what you want to do that is both simpler and secure.