I developed a custom solution for this years ago, a Flash-based PDF viewer specifically to allow viewing sensitive corporate documents without giving employees the ability to copy/paste or to view the full page at any time. I used PHP on the server to run pstoedit -- which can open a PDF and convert any given page to a JPG -- then I piped the JPG as a one-time-use file to Flash. I'm sure the state of the art has vastly improved... pstoedit has a lot of flaws (doesn't handle CMYK PDF files, font files need to be loaded in text format...cannot actually parse the text, so for corporate purposes separate index files had to be uploaded so employees could skip to the right chapter and page...) but it might fit the bill for what you're talking about.