It wasn't individual per install. Anyone with the game manual could find the word or code in the book. Some games asked for a random word from the manual on boot, so you couldn't just share the code, you needed to share the entire manual (or decompile or something to find all the words it is looking for).
And the manuals usually themselves had "copy protection". Many were printed in variations of dark colours, such that any easily accessible copier would just copy a black page.
this was the comment i was looking for! i remember those red pages and found them annoying on even legitimately purchased games (which is how copy protection has always been IME - makes it so legitimate purchasers of a game got annoyed and hence, got cracks for games to just not be as annoyed!)
