I created a Perl application that uses FUSE to embed a mountable filesystem inside of an arbitrary PDF file. I'll talk about the special properties of FUSE and PDF that make this feasible. The software is open source and freely available. I built a Cocoa front-end for it, but I won't delve into that unless specifically requested by attendees.

http://search.cpan.org/dist/Fuse-PDF/
http://chrisdolan.net/yapcna2008/par-fuse-pdf.html