DJVU was better. No, please, not PostScript until you like running a Game Boy emulator in Ghost Script or a ZMachine playing Zork. And you can actually do that with Zork/Anchorhead or whatever IF Z-code game up to v3 version. PS can be crazy for security. It might be good on plan9/9front where you can isolate namespaces and filesystems for free, but not on the rest of the OSes.