Halfmile used to maintain free maps, compiled from public sources and updated by hikers, for hikers. There’s a decent amount of work needed to keep these current. For a number of reasons, they’re no longer being updated.
The new NatGeo maps are nicer, waterproof, and their purchase helps fund the PCT. Something you should do anyway.
If you want to roll the dice with old maps, I’ve archived them here as zip files. WARNING: THESE ARE OLD. I MAKE NO WARRANTY AS TO THEIR SUITABILITY FOR YOUR PURPOSE. I RESERVE THE RIGHT TO TAKE THESE DOWN AT ANY TIME. KNOW WHAT YOU ARE DOING. DONT GET LOST OR DIE. YOU HAVE BEEN WARNED.