Transferring Adobe Digital Editions content between computers

I purchased an ebook in .pdf format and installed it on my office desktop computer about a year ago. Today I've installed Adobe Digital Editions on my laptop, copied the ebook to the laptop, and am trying to read it there. No luck. Every time I click on the book's .pdf file, the computer takes me to the Adobe Digital Editions install page. I've authenticated the laptop in Adobe. The ebook does not appear on my Bookshelf.

Any clues how I access the content that I've already purchased?

Thanks!