Aishi is right. Let's just stop mentioning arrow looping already. It only looks cool, for show, no good in the high levels.
Now, Marth is slightly faster than Pit, and can quickly catch up to him, even when being attacked by arrows. The Pit needs to use arrows sparingly since Marth's speed and range poses a major threat to Pit. The basic Marth spaces with F-air, and that alone is threatening because of its range and spam rate, and it can even destroy arrows.
For the debate on multi-hit moves, Angel Ring is bad. Marth's Up-B comes to play here, should be able to cut through it in no time, should Marth ever get caught in it instead of using his range to knock Pit outta it. For the Infinite Jab, Marth needs to DI outta it, then throw out his attacks, maybe an Up-B too. Now, Marth can't really do nothing against the U-air if he is caught in it, cept trying to DI outta it, though it is very hard to do so. And Pit has basically no use for using N-air in this matchup, so yea.
For recovering, it's only Marth's range that personally hurts, hard to avoid. Trying a glide attack is a regret against a Smart Marth since all he needs is one F-air (or B-air) that outranges all of Pit's moves. If the stage permits it, try gliding under the stage at a very low elevation, not so much where Pit will SD of course. If you are on a stage with no hopes of going under the stage (Both Pokemon stadiums, and YI), then GL trying to avoid Marth. You already know what happens to Pit if he gets hit outta his Up-B, and it's hard to maneuver with a good-ranged character around.
For gimping, Pit to Marth, Marth has his standard mid-air jump, one Side-B to slightly float and stall, Neutral B (Only if he's high up there, where a charged Neutral B will allow him to slide), and Up-B. When Marth is on the ledge, it's hard to surpress him. He can easily just let go and do an F-air, and with that range, he can poke at closeby opponents. He can even try to get on the ledge F-airing. So it is harder than one thinks to gimp him. Pit's best option is to shoot arrows at distance, for Marth's F-air can handle a pursuing Pit, though Marth does have to be cautious with his limited recovery so that he doesn't recover too low.
That's all I can really say atm, but I can round off that it's really Marth's range and speed is what's gonna hurt Pit most in the matchup. Regardless of Pit holding a projectile, again, Marth's speed works here to limit Pit's projectile shooting, and Pit's best option for the matchup is playing defensive, like he does in most matchups.
The matchup is 40:60 Marth's advantage, no more, no less.
Now, if Pit actually found something new that is completely useful, and game-changing, maybe, just maybe, the ratio can change.