World Wildlife Fund (WWF) that's essentially a PDF that can't be printed called a WWF document. It's part of their initiative to save trees and distribute files digitally so they won't have to be printed.
While I like the idea, I highly doubt this will fly. First, it's only compatible with Mac computers (who uses those anyway? :P) second, there will definitely be ways one can print the file. With all the haxors in this world, it's undoubtable.
UPDATE: They now have the software for PCs. Happy tree saving!