Quick question, I want to gift GW2 (digital edition) to a friend, what’s the best way to do it? (I’ll be using paypal)
If I order it on my e-mail address will that cause any problems and can she easily change the e-mail address herself linked to her copy of the game?
I’ll see what I can find out about this.
Here’s what I learned (confirmed by others in this thread):
You can purchase the game using Paypal for your friend as usual. Once your friend goes to register the account, they can do so using their own email address.
In other words, when you purchase the account, you will be given a serial code. Do not use the serial code, but send it to your friend and let him or her use the code to register for a Guild Wars 2 account.
Thanks for being so generous, and for supporting our game with your gifts!! 
