The only legal way to obtain PAK1.PAK is to purchase the game. Verified versions are available on Steam and GOG , which provide the original unmodified PAK files alongside modern remastered versions.
Contains the full "registered" version content, including Episodes 2, 3, and 4. Where to Find Verified Downloads quake 1 pak files download verified
Contains the shareware content, including the first episode, Dimension of the Doomed . The only legal way to obtain PAK1