I think you've fallen into one of the traps that Adobe DRM system lays for its users (details below).
I can only suggest two things:
- Contact the bookseller and see if they are willing to give you a second go with a new .acsm file ~ almost like buying a new copy. I have hears that some vendors are helpful and some are not.
- Try installing a DRM stripper such as EPUBEE (google it) and see if that can remove the DRM from your .pdf.
DRM sripping can be used for illegal purposes such as giving copies of a book to other people. I do not condone any such use.
BUT ... Where the poor user interface of ADE and the aggressively anti-user implementation of the Above ADEPT DRM infrastructure prevent users reading their books in the way intened by the publishers, there is sometimes no other way.
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When you buy a book you get a link to a .acsm file and download it.
You then use ADE (Adobe Digital Editions) to open the .acsm file and download the 'real' .pdf or .epub book;
at that point your copy of the book is associated with the ID in use on ADE at the time.
There is no way to remove that association and associate the book with a different ID.
When you use ADE without giving it an AdobeID, it invents a kind of anonymous/implicit ID.
That ID has very limited uses; eg it can't be used to authorize any other device or computer.
Also, once that ID is 'lost' by reregistering ADE with a 'real' AdobeID, the anonymous ID cannot be recovered.
If you access a DRM book using that ID, the book is associated with the ID.
ADE gives some warnings about running without registering an Adobe ID; but these warnings are not nearly strong enough to give users and idea of the consequences.