My best advice for Marth Vs Pit is to just move in close to avoid the whole Range problem Pit might have against Marth. It also helps to avoid tippers and just instead get hit by his weaker attacks. When your in close you can use your faster attack options, like Utilt, Jabs, and Dtilt. Also using alot of Jabs into Infinite jabs can catch Marth if he likes to spot dodge to Fsmash or something.
During Marths Fair approach, its easiest to either spot dodge or roll behind Marth as hes approaching you.
Use your knock up moves to then go into Uair juggles and you can also use arrows to prolong combos when they get knocked too far. As he is a lot less deadly when directly above you and it most likely the only point in which Pit has the advantage.
Lastly i guess. Try to bait Marths Smashes, which have considerable lag after. Shield and go in for a counter attack.
During Marths Fair approach, its easiest to either spot dodge or roll behind Marth as hes approaching you.
Use your knock up moves to then go into Uair juggles and you can also use arrows to prolong combos when they get knocked too far. As he is a lot less deadly when directly above you and it most likely the only point in which Pit has the advantage.
Lastly i guess. Try to bait Marths Smashes, which have considerable lag after. Shield and go in for a counter attack.