Call Marriott Rewards Guest Services and let them know you have a paper certificate for your stay and they will note it in your reservation. Also for anybody like myself, who orders certificates well after the point in time they made their reservation, you should call Marriott Rewards Guest Services and have any outstanding electronic reward certficiates connected to appropriate pending reward reservations. I just got through doing that for my 3 weeks at Vail next year.

This new enhancement now connects ordered certificates with the stay for which it was ordered. A big improvement IMO. I was always fearful that the wrong reward certificate might be used for a reservation. Now that they are, or will be, connected to a specific reservation there is no worry.