Well the biggest one: there's an entire "Sandy Petersen's Cthulhu Mythos" volume for PF1. Few hundred pages, I know James Jacobs contributed a bunch to it. Really good book.
I think it might be easier listing the books that DON'T have Cthulhu references to be honest.
All of Strange Aeons is probably loaded. Book 5 of Carrion Crown, too. If not Cthulhu directly, definitely mythos stuff. Also, Occult Realms and Distant Worlds both talk about the Citadel of the Black on Aucturn, which is dedicated the the Great Old Ones.
At the very least, you will get a lot of Mythos stuff all over the place.