No, printing a paper copy of your parking reservation is not required. You can present your digital voucher on a mobile device.
If you have trouble accessing your voucher, you can provide the 9-digit barcode number to the parking attendants. However, if you have pre-purchased park entrance fees, you must have a voucher (digital or printed) to present at the visitor center.
To retrieve your voucher, click here and enter your barcode number and the date of your visit. You will have the option to download your reservation to the device you are using.