When you download Adobe-DRMed eBooks for the first time, you will be asked to authorize your device with an Adobe ID. Authorizing your device is necessary in order to read Adobe-DRMed eBooks. However, you can still enjoy downloading and reading non-encrypted EPUB and PDF eBooks if you decide not to authorize your device .
To authorize your device, just tap on the navigation drawer indicator at the top left corner to go to navigation drawer, select “About”. After that, tap on “Adobe DRM”. If you have an Adobe ID already, just type in your Adobe ID and Password and then tap on “Sign in”. If you don’t have an Adobe ID, just tap on” Register” and you will be linked to Adobe’s registration page, or you can go to Adobe website here (https://www.adobe.com/account/sign-in.adobedotcom.html) to register one.
If you decide not to authorize your device now, you can always do so it at a later date.
Please note that Adobe limits your total amount of authorizations. Each time you authorize your device with an Adobe ID, it counts against your total number, even though you do it on the same device.