A defender who initially joined Town on a loan deal from Barnsley until the end of the 2015/16 season, although that deal was later made permanent.
Paul worked his way through the ranks with the Tykes and made his debut at the age of 16 in a 1-1 draw with Derby in 2011.
Made his Town debut in the FA Cup against Portsmouth before making his first Championship appearance in a 0-0 draw with Middlesbrough at the Riverside Stadium.
He has represented England in a range of different age categories, and has trained with the first-team on occasion.
'Diggers' will wear the number 14 during his time at Portman Road.