I have a .acsm file on my computer. Whenever I click on this file, Adobe Digital Editions opens and goes through a lengthy download process. At the end of the download process, I have a .pdf file on my computer. Each time I open the .acsm file, I get a new version of the .pdf file with roughly the same name (a dash and an integer get appended to the name).
If I try to click on one of the .pdf files directly, a dialog box opens with the following message: "This document requires digital rights management (DRM) features supported by Adobe Digital Editions. Would you like to open it in Digital Editions now?"
If I click on "OK", my browser opens the following URL: Adobe Digital Editions This page displays general information about ADE, which I'm not terribly interested in seeing. The book does not actually open in Digital Editions. If I click on the .acsm file, I get yet another .pdf file downloaded to my computer.
The following applies to windows (it might to MAC as well).
1. In My Documents is a Folder My Digital Editions, all downloaded books should be there.
2. Open ADE. All the books in My Digital Editions should show in Library View. Double click on one to open it. If you find multiple copies of the same pdf you can individually delete the extras either from ADE or using windows explorer.