Pearson came through at United with Harrop.
He told pnefc.co.uk: “I've known Josh now for 12 to 15 years; he was a year below me when I was at Manchester United. We played in the same youth team and in the reserves - so I've played with him a lot - I know him well and I know him well off the field as well.
“He's a good lad, a good player and a big character in the changing room. He knows what it's about playing at this level - he knows he needs to leave now to get proper game time.
“He'll be hoping to bed in with the squad now and I think he'll be a real asset. He's got good quality with the ball and without the ball, he works hard and he'll give his all."