Print whatever they send. Print it: it is worth the effort: you will not convince the police with a phone but you might with a paper.
Digital is OK until you run out of battery or anyone refuses to accept your phone as proof.
When you hire a car you are just hiring a several-thousand-dollars item from a stranger. Either you take it seriously (and have a paper trail, hence) or you do not understand the risks.
I recently read of some hapless tourists who rented a car, parted it at a trailhead in the Santa Cruz mountains and when they got back from their hike it wouldn't start because it couldn't contact the mothership.
Seriously should be a felony to posses a device designed to remotely shut down an automobile.
