If you pre-ordered from SE you probably did get a code your just not looking in the correct place. On the page where you downloaded you PDF file there is a code in the next paragraph.
From your order confirmation email go to http://www.findmyorder.com
Under begin download there is a serial # for an electronic download. then the Instructions.
Instructions to sign up for early access to the game:
and register. You will be notified via email prior to the launch of the game on when you can return and redeem your preorder code to unlock Early Access to the game along with instructions on how to receive your Cait Sith Doll minion and Moogle Cap digital content.
You will need an active Square Enix account to complete this process so, if you want to set one up in advance, please go here: http://na.square-enix.com/members. Edited, Jun 8th 2013 10:08am by Strifefish