Often, they are. Please check for the e-ticket sign on the trip.
Sometimes, you must show the voucher at check-in to get the boarding pass.
In other cases, operators require passengers to print the voucher and keep it as a ticket during the trip or exchange it for a paper ticket at the station. We have no control over these rules and can’t affect the carriers’ procedures.
Some operators will check your ID before boarding: passport, driver’s license, student card, or any other government-issued document will work. Failing to provide those or a mismatch in the numbers may be a reason to deny boarding.