For the life of me, I cannot understand the logic of this. I need to take my GAD vouchers to a ticket window, get a one day ticket, enter the park, and then when I leave the park I go back to Guest Relations to upgrade to an annual pass?
Disney ticketing is a weird process with lots of weird rules, but for the most part they make sense.
As far as the GAD ticket goes, one of the rules is that you must use the ticket on the day you redeem the voucher. If you just redeem the voucher for a 1 day ticket that's easy... they just put a 24 hour expiration on that ticket. But, because you can also upgrade that ticket to a regular multiday ticket it gets a bit tricky. Regular tickets don't expire until they're used and they don't want you to get the GAD ticket and upgrade it to a regular ticket and then not use it for several years.
So they made upgrades a two step process. You must first redeem the voucher for a one day ticket and use that ticket to enter the park. That ensures that you have entered the park with the ticket. Then you can upgrade the used ticket to whatever you want. Whenever you upgrade a Disney ticket you'll get full credit for the value of the ticket, but the computer will see it as though you had the upgraded ticket from the start. For example, if you use your GAD ticket to enter the park, then upgrade to a 5 day ticket you'll get full credit for the value of a one day ticket ($79, plus tax) for the GAD ticket, even though it was used, but the 5 day ticket you get will also have one day used on it and four days left. The same as if you had bought a 5 day ticket in the first place and used one of the days.
Now, all that said, from what people have reported here (and my own experience), if you want to upgrade your GAD ticket to an annual pass or an annual pass renewal then you can do that all in one step when you redeem your voucher. Since the AP does have a built in expiration date it doesn't really matter if you enter the park with your GAD ticket first or not.
Finally, there is one more weird ticketing rule that comes into play when upgrading regular tickets, and that is that a partially used ticket (one that has been used to enter a park) will get full gate value toward an upgrade whereas an unused ticket will only be worth what was originally paid for it. If you just bought a ticket at the gate then this doesn't really matter. But if you have an older ticket that was bought before a ticket price increase, or a ticket that was bought at a discount then you'll get more money toward your upgrade if you use the ticket first. That's why we always recommend that you use the ticket before you upgrade it.