Is this possible? I did research, and I found multiple people on forums saying that this is possible, but they don't explain how.
Load Steam. On the bottom left there is an "ADD A GAME" link. Click on it and click on "Activate a product on Steam..."
Click NEXT, then I AGREE, then enter your "Dragon Age Awakening" NON-steam key. It should activate on Steam, and you should be able to download it from there as well.