Handwriting expert.
There is no doubt that handwriting expert or forensic document examiner is the only professions that will help you check and examine the document whether it was original altered or forge. Document examination is very vital especially if you work with case that involves the documents.
The work of forensic document examiner is obviously involving wider aspect in writing. They will not only work with ink from a pen or looking clue from paper and other mechanical device like copier, printer and type writer that can provide any clue, but they also analyze any marking that present in the document in question. So if you are in doubt about particular document, hiring handwriting expert should be the right action.