adobe digital doesn't require ID on computer, messes up activating it on my ipad?

The work computer I have doesn't require an ID on adobe digital.  However, when I go to add the book to my ipad via the millenium ereader it prompts me to log into adobe stating, "this item was originally downloaded with a different user account or Adobe ID. To continue, please add that account."  The problem is I didn't log into any account on my work computer?  Please help!  I'd rather access the book on my ipad than on the work computer.