Download, full document: An Adobe ID - what it's needed for and how to get one

You need an Adobe ID to open a downloaded ebook via Adobe Digital Editions (on a computer), Bluefire (on a device), or using any other Adobe DRM compatible reader. It is possible to download and read books in Adobe Digital Editions when authorized without an Adobe ID, but you can only share documents to another device if you have both devices authorized to the same Adobe ID.  You can activate up to six computers and devices. If you authorize ADE without an Adobe ID, any books downloaded will be limited to that single device. Bluefire Reader always requires an Adobe ID for authorization.

To create an Adobe account:
  1. Go to accounts.adobe.com
  2. Click “Get an Adobe ID”
  3. Fill out the form
  4. Click “Sign Up
Your Adobe ID will be the email address you used to sign up.