Hi ppp123,
In case you signed a form, stating you're intended to live and work in a particular Province, you're still eligible to move anywhere, but once you'll decide to get Canadian Citizenship - additional questions will arise.
I know that it's strictly recommended by more experienced former PNP nominants to live in a Province that nominated you as long as possible, even if no job has been found during this period. Also, it worth to ask PNP officers to allow you leaving this province - their reply will be good point if there will be some complications in getting citizenship.
I heard one story that PNP nominant has moved from BC to Alberta due to some medical complications with his wife (wet climate wasn't good for her asthma) - they had to prove that, since their citizenship application has been put on hold.
If you're moving to another province in some weeks after getting your PR - that could be considered as the immigration fraud. And, frankly speaking, it is indeed. But if you're able to prove you had to move as no job has been found in some months or by other reasons - I don't think it's really critical.