You have to buy them due to copyright that Mondial Group has on Gottlieb IP
Why do the Gottlieb files all say Availability limited by copyright?
To protect their copyrights and trademarks and therefore protect the income of their licensees, Gottlieb Development LLC has required that we remove all Gottlieb manuals and ROMs from the site (even though – in our opinion – this just makes it harder for owners to determine part numbers needed to order licensed parts).
Gottlieb manuals, ROMS, and other parts are available from several officially licensed manufacturers:
Steve Young's 'The Pinball Resource' is a source for paper Gottlieb manuals and other mechanical parts.
John Robertson's 'Flippers.com' is a source for Gottlieb EPROMs, PROMs, PALs, 6530 replacements, and other parts for Electromechanical and Solid State games.
A list of additional licensed manufacturers can be found at Mondial International Corporation. http://www.mondialgroup.com/gottlieb.htm
Go buy one