Can you add a day to Disney tickets purchased not from Disney?

[100acreHiker]

Sorry if this is stupid question--only ever purchased packages direct from Disney. Does anyone know if I purchase 5-day base tickets from another agency (like through a family member's work discount) and link them to my MDE account, is it possible to add a day to these tickets during our trip at our Disney resort or at a park gate?

 

[Dan Murphy]

You can if they are regular tickets. If they are some sort of a special ticket, then generally no.