PDFs on Adobe Digital Editions 4.5

Hi Jane, Adobe's email prompt has just reminded me that I never got back to you or the forum about this.  I did read the articles on Kobo's website and also contact Kobo as you kindly suggested, but unfortuately couldn't make any headway.  Kobo's help person told me that the problem was most likely with Adobe and that they couldn't help any further.  The only glimps of a potential explanation and solution I wondered about from reading the articles on the Kobo website was whether the fact that the pdf I was trying to add had the end to the file name (apologies for lack of tech language here!) 'pdf' rather than 'acsm' was the reason it wasn't working.  I emailed the company I purchased the pdf book from to ask about the availability of a file format ending in acsm and they said that was the format ending in 'pdf' was the only format they had for this particular title and, whilst they did say that they would raise the issue higher up in case there might be a solution, they also offered me a refund if I was unable to read it on the device I wanted to.  In the meantime, I discovered a way to add the book to my kindle rather than my kobo, so I've bypassed the problem (and didn't need the refund).  I'm still left confused as to why I couldn't get the PDF book onto ADE and would be interested if you or anyone else have any further explanation or suggesions, but no worries if not.  I am able to read the book on my laptop via Adobe Acrobat reader, but this doesn't solve  the issue of how to get the book onto my Kobo for which (as I understand it at least) ADE is neccesary.  Thanks again for your help and no worries if you can't help further.