It was Preston's heaviest loss at home under Billy Davies and only his second home league defeat as manager, in a run stretching back to November last year.
The Lilywhites had the first chance after 15 minutes when a Paul McKenna corner was headed over the bar by Richard Cresswell and three minutes later, he sent another header too high.
Reading took the lead after 34 minutes when Lita scored from 12 yards, right-footed into the roof of the net after a cross from the left from Convey. The England Under-21 international was a £1million summer signing from Bristol City and also scored last week on his league debut at home to Plymouth.
Just before half-time Chris Sedgwick's right-wing cross fell nicely to Cresswell, but he slipped and the ball bounced kindly for visiting goalkeeper Marcus Hahnemann.
Preston captain Chris Lucketti then sent headers over and wide from successive McKenna corners.
Lita made it 2-0 after just 17 seconds of the second half when he hit an eight-yard shot right-footed beneath home goalkeeper Carlo Nash, after a long ball over the top by Convey.
Callum Davidson was booked for Preston for a foul on Glen Little after 53 minutes, but it was the former Burnley man who made it 3-0 to Reading four minutes later.
He met a Nicky Shorey cross from the left and planted a header into the roof of the goal.
The home side pressed hard in the closing stages but Hahnemannwas in fine form to deny substitute Danny Dichio three times and keep out a Graham Alexander free-kick.