You need to be much more specific as @Michael Bullo already pointed out before anyone even can advise on the potential of a forensic analysis. Different formats require different approaches. If all you have is soem low-res photos of a paper contract then that's pretty much a pointless venture, but a high-res scan may expose tampering. Similarly, if someone hacked around in a PDF this can be detected, but other formats may not. Rinse repeat for whatever you have in mind.