Once you have bought the ticket
You will be able to download them from the confirmation page. Moreover, you will receive an email with your ticket and some additional information, such as the PNR Code, a change reservation link (if the fare allows it), and the details of your carriage, place assigned, date and time.
Once on the train, you will only need to provide PNR to the crew.
If you have lost or forgotten the receipt of payment or the PNR you will be considered without a ticket and therefore you will be required to pay the ticket and the expected fine in a case that you can not prove that you have a valid PNR.
Therefore we recommend printing the ticket.