Nebulous
Legend
It may not be difficult, but it would be tedious. Looking up and recopying stats for every monster, converting every NPC (sometimes when the Pathfinder materials use PF material that does not have a clear analog in 5e), revisiting every DC. It'd probably get old fast.
And, it would probably work well for the low end of the Pathfinder scale, but the high-end might get tricky. 5e has bounded accuracy, PF does not. The conversion then does not become obvious.
Magical treasure, as well, will be a problem - you'd expect a lot more of it in PF than in 5e. Making sure the characters are rewarded suitably, is then non-trivial.
Yeah, i wasn't even thinking of high level adventure conversion, that would be very time consuming and considerably more difficult. I was thinking more along the lines of 1st-5th level i guess.