All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Earning one's livelihood by forging documents, certificates and the like of that is an evil source of earning as it is forbidden to cheat, make false testimonies and lie. As a matter of fact, the Prophet said: "Whoever cheats is not one of us." [Muslim] Moreover, the Prophet said: ''…and a man continues to tell lies till he is written before Allaah, as a liar." [Al-Bukhari and Muslim] For more benefit in this regard, please refer to Fataawa 84658 and 87821.
The person you inquired about tells lies, forges documents and cheats by statement, action, and writing, which causes a great evil. Therefore, this man is obliged to fear Allaah and immediately stop doing this job. Besides, he should seek his provision from permissible means and they are so many.
Thus, the earning of this man from this job, is considered ill-gotten and he is not allowed to own it. His earning is like the earning of a magician, or a prostitute, or other similar earnings which one gets from a forbidden source.
Consequently, this money should be spent on public utilities of Muslims, like orphanages, nursing homes, or may be donated to the poor and destitute.
Allaah Knows best.