Theoretically, they just scan the code, and you should be fine with one.
After all, if you have the ticket image on your device, they will just scan it straight off the device and no printout is involved at all.
However, I have had them lift the printout in the past, and I am a cautious person, so I usually make one extra "just in case." Probably going to stop doing that soon, as even our little AmBus that connects from Bend to Chemult now uses scanners.