The ex-Palace, Ipswich and Sunderland player had been training with Preston for the past few weeks. As a free agent he could sign for any club despite the transfer window being closed.
Wickham has had injury problems over a number of years which have restricted his number of appearances and also explains why he was without a club.
Preston were always looking to beef up their attacking options and Wickham came off the bench in the game against West Brom. He will need to get up to speed with his fitness.
The deal is not so much of a gamble but an opportunity for both parties. Wickham will want to show that he is still capable of playing and scoring at Championship level which could net him a better deal whilst Preston are only tied in until January should Wickham stall in his tracks.