Preston boss Darren Ferguson told BBC Radio Lancashire: "The thing about Iain is he knows the league well - he's always scored goals."
"He can play right wing, left wing and up front. He's a good player."
Hume joined Barnsley in 2008 but has netted just nine times in 55 appearances after struggling to get a regular run in the side.
His first season was curtailed by a horrific head injury suffered against Sheffield United.
I'm afraid Hume is yet another signing no longer at Championship standard. dawsonsjs "There's no gamble here, some people might talk about his injury but no, that's not a problem," Ferguson added.
"He's a player I've always admired -whenever I've played against him he could cause you problems.
"For whatever reason he's out of favour at Barnsley - I just think he needs a fresh start especially after the injury and everything - we're delighted to get him."