Hi, Renee!
Welcome to Walt Disney World! You can certainly upgrade your existing park ticket to an
Annual Pass. Simply take your ticket to any Ticket Window and a friendly Cast Member will be happy to give you the cost to upgrade and make your changes. Make sure the new Annual Pass is linked to your My Disney Experience account and you are good to go. (If you already starting using your park ticket, but have days remaining and are within 14 days of ticket's first use, the balance of your ticket can be applied to your new Annual Pass.)
A Walt Disney World
Annual Pass has many benefits including shopping and dining discounts. Benefits are always changing, so I automatically ask if they honor the Annual Pass discount at all locations. To receive any discounts, you must present your Annual Pass card and your photo ID so make sure to keep those both handy.
Your idea to upgrade your ticket is a great idea. I have an Annual Pass, and I am always pleasantly surprised how much I save with my discounts. Of course my husband says it is because I shop too much while on vacation but that is a whole different conversation!
Another fun perk with the Annual Pass:
Disney PhotoPass downloads! Stop for those PhotoPass photographers and say CHEESE to capture all the magic!
Wishing you a year full of fun with your Walt Disney World Annual Pass.
Cathy