If you are using an Apple device you can download an ebook in PDF or ePub format protected with Adobe Digital Rights Management (DRM) to the Apple device using the Bluefire Reader app.
Simply install the Bluefire Reader app on your iPhone/iPad/iPod. Then touch on the app and you will be prompted to authorize the app with your Adobe ID (you only need to do this once).
You are able to download or transfer the same ebook to up to 6 computers and devices.