Are there ever any situations in which evouchers have to be printed on paper anymore? To upgrade on UA, for example? If so, what is the process? Can vouchers be printed for use against bookings yet to be made, e.g. if one is heading to the US but does not yet know internal travel plans, or for standby use, etc.?

If they are printed and then recredited for future use as evouchers, is the process difficult and are there any fees?

Thanks.