Term for putting someone else's name on one's work?

Such texts are called pseudepigrapha; the adjective form pseudepigraphic is a little more common.

I agree with Jim. The correct word is "forgery". "Pseudepigraph", "fallacious co-authorship" or (specifically with reference to the "later letters of Paul") "deutero-Pauline" are all euphemisms.

Perhaps "creation of apocryphal documents".

The adjective "apocryphal" applies to written works, that are of unknown or questionable authorship, of doubtful authenticity or spurious.

I am not totally satisfied by this proposal, because texts are said apocryphal by the readers a long time after their writing. I didn't remember having seen this word used for the production of the text.