Emil Riis netted a 95th minute equaliser for the Lilywhites, time almost up when he fired home Jordan Storey' s cross.
Daniel Johnson had scored in the first half, the PNE skipper levelling the game up after Morgan Gibbs-White's early opener.
The Blades regained the lead in the 84th minute through Sander Berge before Riis' late intervention earned the visitors a point.
Here are the PNE player ratings from the clash.
1. Daniel Iversen 8
The PNE goalkeeper made a great late save to deny John Fleck in a one-on-one. Berge's goal went through his legs but was struck with power. Photo: Alex Dodd, Camerasport
2. Jordan Storey 7
Decent display at the back against a lively United front line. Caught stepping out for Fleck's chance which Iversen saved. Photo: Alex Dodd, Camerasport
3. Patrick Bauer 7
The German centre-half gave the ball away for Sheffield United's first goal but recovered to have a steady enough game. Photo: Alex Dodd, Camerasport
4. Andrew Hughes 8
Really strong game on the left side of the back three for the Welshman. Defended really well. Photo: Alex Dodd, Camerasport