Anel Ahmedhodžić put the Blades into the lead, who were promoted in midweek, with Liam Delap getting North End back on level terms.
The home side ran away with the game however, John Fleck, Iliman Ndiaye and Ali McBurnie all adding second half goals.
It means that Preston can no longer reach the top six, mathematically, after a poor day in Yorkshire.
Here’s how we rated the players on the day...
9. Josh Onomah - 5
Another midfielder that looked laboured, the game time and lack of fitness might be catching up to Onomah whose bright moments have become a bit more fleeting. Photo: CameraSport - Rich Linley
10. Alvaro Fernandez - 6
Gave his best down the left but was generally well matched by Jayden Bogle down United's right. Wasn't able to influence proceedings very much. Photo: CameraSport - Rich Linley
11. Tom Cannon - 5
Made some wrong choices on the day and just seemed determined to shoot every time he got the ball rather than looking for others who might have been in better positions. Was pushed out to the left in the second half and did his tracking back well. Photo: CameraSport - Rich Linley
12. Troy Parrott - 5
Another tough day for the Irishman who seemed to draw the ire of his manager in the first half. He was in the middle of a front three in the second half but couldn't be much of a foil. Had a big chance at 3-1 to get North End back in the game but couldn't take it. Photo: CameraSport - Rich Linley