What about the Office Document Imaging app that creates MDI files? I swear you can print a 1 meg Word doc to it and it comes out less than half that! That's better than PDf and smaller than Zipped. It maintains all formatting as well.
It's easy to import TIFF (fax) files as well and works hand-in-hand with Outlook 2003 and online fax services.
I think it's definitely better than PDF but there's no editing functionality (which I don't need anyway).