The Grecians should have been behind after 23 minutes at Deepdale on Saturday when Steve Tully was sent off for bringing down Neil Mellor inside the box but Graham Alexander saw his penalty saved by Artur Krysiak.
The Polish goalkeeper was beaten four minutes before the break though when Proctor headed in Paul Parry’s free-kick to condemn Exeter to a third defeat on the spin.
The Grecians’ hopes of upsetting the form book in League One suffered a huge blow when Tully was red carded for a professional foul on Mellor inside the box.
Alexander uncharacteristically spurned the resulting penalty – hammering it straight down Krysiak’s throat – but the 10 men failed to hold out until the break.
The Lilywhites struck four minutes before half-time when Proctor headed home Parry’s free-kick, with James Dunne’s deflected shot which struck the bar the closest Exeter came to levelling in the second-half.