Adobe digital assistant

I have a new 7 in nook tablet & I want to download epub books to it which I've picked up from sites other than Barnes & Noble. I'm told to do so I need adobe digital assistant but not version 4.5 but 3 something or other. However, I don't see any option for other than the 4.5 which doesn't appear to work with the nook BNTV 460. Seems like an awful lot of effort to read anymore as my previous look I could just plug it into the computer and copy files to one of the sub-directories. In the new one, only the root directory is shown.

Thanks for any help as B&N have not been any help

Dave C