The goals came in the first half and Dunfermline's hope ended in the second when Chris Kane was sent off for a second booking.
Arbroath took the lead after seven minutes when Stevie Milne collected his third goal of the season.
Callum Morris equalised on 27 minutes before Shaun Byrne put Dunfermline in front.
But Arbroath's Alan Cook scored from the spot after Kane was penalised, then added a fine individual goal.
Stenhousemuir beat Airdrieonians 1-0 away from home with Ross McNeil scoring the winner.
Airdrie's Lewis Coult saw a tame penalty saved by Chris Smith in the second half, and Stenhousemuir's Ross McMillan was sent off for his second booking.
Ayr United beat Forfar Athletic 2-0 at Somerset Park with Craig Malcolm and Michael Moffat scoring.
Moffat's 75th-minute goal came from the penalty spot after Darren Dods handled, resulting in a red card.
Second-half goals from Ryan Donnelly and Alan Trouten were enough to give Brechin City a 2-0 win at home to East Fife.