The striker left Rangers at the end of the season after his contract wasn't renewed and has now put pen to paper at Deepdale.
And Preston boss Simon Grayson is delighted to bring the Northern Irishman on board as they target promotion to the Championship this term.
Grayson said: "Andy has a fantastic goal record in Scotland and he can handle playing for a big club, as he has shown with Rangers.
"He is also an international player. He is good age and has some good qualities that we are looking for in the squad.
"He will bring real pace to the striking department and that is something we have been looking to add and I am delighted that he has chosen us over quite a few other teams.
"Snods [Glynn Snodin] has worked with him before, with Northern Ireland and Billy McKinlay who is the assistant there has also given him good reports.
"We have had games watched in Scotland and he fits into the balance of the squad we are trying to create here."