Pretty easily. Games back in the 80's would have, as an example, 30 pages of random words in the game's user manual. Each time you start the game up, it'll ask you for Page x, line x, word #x. You'd have to get the manual and look it up in order to play.
It was cake to throw in a blank floppy and copy the game for your neighbor.
However, the book made it slightly more difficult. Well, what's stopping someone from photocopying 30 pages of random words and including it with the pirated floppy? Those pages were printed on very dark gray paper so copy machines would spit out solid black pages instead of copies of the book. :awe:
Mofuckas was smart back inna day!
Oh wait, all it took was someone taking 15 minutes to open Notepad and type them all out, THEN print it.
DOH.