You do not need to print your ticket, but the printed one works just fine.
After your tickets are bought, you will receive a confirmation letter to your email. There you will find your ticket's QR code integrated into email. The QR code is the one you have to show at the registration point at the Opera House to receive event's badge and bracelet.
No printed tickets are needed, however, if you like having physical tickets, feel free to print the PDF ticket attached to your ticket email.
Also, if some issues appear with the ticket assignation, it is better to have your ticket in your email, so you could fill-in or change your details in this form on your phone.
What is ticket assignation? All information here.