My friend is a decent pit. I still destroy him.
Arrows are a pain, but jumping/fast falls work well to get close. However, the closest you should get is the range of your f-tilt. Pits usually set up on the edge of the stage to shoot arrows, so they wont be able to roll away from f-tilt.
Pit's forward and down smash are two hitters, but shield grabbing after the first hit works wonders. Grab Pit to death.
Your ftilt generally has priority over his over-b.
After you throw Pit into oblivion, they'll usually try rolling if they can't spam B moves. If they roll behind you, Dsmash. in front, Dtilt.
Pit's recovery is easily gimped if you get him under the ledge. He can only use his Up+B once even if he gets hit, so if you edgehog and he uses it, hit him with a bair and he'll fall to his doom.
As someone mentioned earlier, fair juggling works, aswell as bair.
And last but not least, throwing waddles while jumping and fast falling can counter arrows if your decently accurate. One waddle hit will be able to get you close enough.
Hope this helps.