Pagefair is basically "Clean ads as a service." If they detect your using Adblock plus, they'll server you an ad, adblock plus won't block, because they pay adblock plus. (And because they claim to follow adblock plus's policy of 'good ads').

Which is annoying, because if you aren't using adblock plus, you don't get decent ads (just the standard ads), so ultimately it defeats the goal of adblock which is to make all ads non-obtrusive, for all users, not just the chosen few who use adblock.

Adblock edge will block pagefair ads, because adblock edge is a not-for-profit adblocker, unlike adblock plus.

Also hosts blocking remains a completely viable option.