Ok, here we go, files are attached, Lemmings and ONML. The manual for Lemmings had the codes printed in an extremely faint green, by what must have been the world's worst dot-matrix printer, so I have transcribed the information into the separate spreadsheet for ease of use. The manual for ONML was better and the codes are visible straight out of the book.

Hi everyone, I can see this is a fairly old trail, but I may be able to help if anyone still needs these security codes to activate your games. I'm in the process of bringing an old Apple G4 iMac back to life with one of the early operating systems (OS9) just so I can play some of the games I used to enjoy. I have the manuals and codes for 2 versions of the game; Lemmings and Oh No! More Lemmings, along with some other generic paperwork about installing and playing the games. The books were all copyright of Psygnosis, but since they no longer exist I'm not sure what the rules are about distributing the info. Happy to discuss/chat with anyone who needs this info.