They were PDF tickets at Juventus last month, and belive it or not, the stewards would scan your ticket and the name would show up on their screen, meaning changing the PDF didn't make a difference.
A few hundred blues didn't make it in to the ground because of that.
The difference with that was that the club gave us plenty of notice, and made it very clear there'd be checks before you purchased the ticket. This time they've just sprung it on us 6 days before!