The Lilywhites struggled to get to grips with their visitors and also with a strong wind which made for testing playing conditions.
Fidel O’Rourke and Tom Clayton found the net for Liverpool in the first half, with Jack Bearne stretching the Reds' advantage six minutes after half-time.
North End’s best chance of the game was a shot from Josh Murphy which clipped the outside of the post but otherwise they created little.
There was a mix of ages in the PNE side, Paul Huntington skippering the side, while Sean Maguire played 45 minutes of his return from damaged ankle ligaments.
Murphy played the full game as he pushed for match fitness after his return to action last weekend, while Matthew Olosunde featured on the right hand side of a back three.
Liverpool had Preston-born Rhys Williams in their back four, the 21-year-old having played 19 times for their first-team last season.
Conor Bradley, 18, who has already been capped at senior level by Northern Ireland, operated at right-back.
PNE operated in a 3-5-2 system and had Paul Gallagher in the technical area, although Ryan Lowe was there keeping a watchful eye on proceedings.
Mikey O’Neill put an early shot into the side-netting but Liverpool got control of the game and bossed it from there.
They went in front after 25 minutes, Olosunde’s foul on O’Rourke giving away a free-kick just outside the corner of the box.
Leighton Clarkson delivered it to the far post where O’Rourke provided the finishing touch.
Murphy’s shot after he latched on to a pass down the right channel, hit the outside of the post in the 34th minute before Liverpool got their second goal six minutes before the interval.
James Norris’ cross flashed across the box and came out to Bradley on the right, his cross back into the middle finding Tom Clayton who headed home.
Their third came in the 51st minute as North End tried to play out from the back and evade the Reds’ press.
Josh Seary lost possession and Jack Bearne ran through to shoot past Connor Ripley.
O’Neill was close to reducing the arrears with a shot on the turn which went wide.