Well, as much as I'd love to believe him, I can't. I start immediately asking questions, like, why is every word either all caps or start with a capital letter except for the word "negative"? Could be the way that lab does it, but almost nowhere else seems to.
There are similar documents you can find online and they all look pretty similar, from comparing them, I'd say the document itself is authentic, although that tells us nothing but that the pdf does come from a lab that does drug testing and that it has his name on it. We don't know if it was his urine, or if he paid to have a clean report or anything the like.