I can say for sure that this document is authentic.

Solution (By Examveda Team)

Authentic : of undisputed origin and not a copy; genuine.
Fictitious : not real or true; imaginary or fabricated.
Duplicate : exactly like something else, especially through having been copied.
Fallacious : based on a mistaken belief.
Erroneous : wrong; incorrect.

Antonym of Authentic is Fictitious