Google found this thread when I was looking for a solution to the same problem. After trying the recommendations here with little success, I found a freeware program that converts directly to epub with better results than the others. Here's the link -
PDFMate Free PDF Converter.
Two things to be aware of before installing this. One, by default it will modify all your browsers to install a toolbar, default search, and other crapware. Prevent this by selecting Custom install and un-checking all the boxes. Two, it nags you to upgrade to the paid version every time you convert a file. If you can live with this, try it.
Disclaimer: I am not associated in any way, shape, or form with PDFMate, either directly or indirectly. It gave decent results converting a two-column PDF to epub. That's all.
Two more points from my experiments. One, about cybmole's technique of pasting into Word: in Adobe Reader, "Copy / Select All" gives poor results, while "Copy File to Clipboard" gives good ones. Two, when I tried using Calibre's new PDF conversion engine from the command line, I got a bunch of Python error messages.