The Pittodrie side were marginally better in a disappointing first half in Tayside but allowed United to grab the initiative when John Souttar benefited from Jamie Langfield's mistake to head the Terrors ahead in the 50th minute.
Barry Robson levelled the scores with a spot-kick 15 minutes later before Pawlett teed up a dramatic finish with his header beyond the excellent Radoslaw Cierzniak in the 90th minute to ensure his team stay just two points behind the Steelmen in the Scottish Premiership standings.
Jackie McNamara's men have followed their six-match winning streak with three defeats in a row and trail the Fir Park side by eight points.
They were hopeless as they were cut down by St Johnstone on Sunday. The manager had made eight changes to his team for that Perth fixture but showed his anger at the 3-0 defeat that followed by making another seven for the visit of the Dons as Souttar, Gavin Gunning, John Rankin, Gary Mackay-Steven, Ryan Gauld, Stuart Armstrong and Nadir Ciftci all returned to starting slots.
Aberdeen boss Derek McInnes, meanwhile, recalled Russell Anderson and Robson as he named his strongest line-up.
A sell-out 14,00-strong crowd turned out in anticipation of an enthralling battle between two of the most talked about teams in the country.
But nerves were apparent from both camps during the early exchanges as move after move broke down without a climax on a skiddy surface.
A foul by former United midfielder Willo Flood on Mackay-Steven just as the winger looked to break clear on the halfway line did bring a howl of derision from the furious home support, clearly still tetchy following Flood's summer defection, and an early booking just 16 minutes in.
Finally, with half an hour gone, an opportunity of note did materialise when Pawlett robbed Souttar as the defender dawdled on the ball 25 yards out, but even then Cierzniak was able to beat the midfielder's low shot out for a corner.
Niall McGinn took care of the set-piece that followed but the Polish stopper was less sure with his attempt at a punch and was relieved to see Andrew Robertson boot clear after the ball dropped dangerously towards his own net.
Paul Paton was required to produce a last-ditch challenge on Scott Vernon after Ryan Jack had sent the big striker galloping through on goal four minutes before the break, while Robertson's deflected strike had Jamie Langfield scrambling in the Reds goal before it eventually planted itself in the side-netting.
Having made that raft of changes to his starting line-up, McNamara could be forgiven for wishing to make another seven at the break.
The likes of Armstrong, Gauld and MacKay-Steven have been linked with interest from some of Europe's biggest club but they were smothered time and again by the Dons.
Aberdeen continued to look the more likely side to score at the start of the second half as first Gunning had to block from Pawlett six yards out after the central defender failed to clear McGinn's cut-back.
A second attempt by Pawlett was then only stopped by a fantastic instinctive save from Cierzniak seconds later.
But with their first real opening, United grabbed an undeserved lead.
Mark Wilson's corner from the left was swung in with menace. So good in fact it caught out Langfield, who came for the delivery but got nowhere near it, leaving Souttar an empty net to aim his header into.
The goal was obviously the ingredient the game had missed in the first half as it immediately livened up proceedings.
Paton collected a booking four minutes before the hour after his flailing arm caught Pawlett in the face but survived earning a second five minutes later after sliding in on the same victim.
But Aberdeen got the reward for their first-half efforts in the 65th minute when referee Willie Collum judged Robertson to have handled in the box after Robson's through ball skipped up awkwardly towards his armpit. Robson took the penalty himself and careered the ball into the top corner with an emphatic strike.
Cierzniak was outstanding again with 13 minutes to go when he sprang to his left to push away a curling shot from McGinn but was undone after spilling Robson's free-kick just as the game moved towards injury time.
The ball sat up perfectly for Pawlett who dived head long to send it into the net and clinch the three points.
- Sports & Recreation
- Jamie Langfield
- John Souttar