Acrobat will also convert directly to .rtf, docx, etc. This is rarely an improvement tho.
One secret I learned in this forum (I think) is to open the .pdf in MobiPocket Creator. This free software will convert the .pdf to an html file. Import that file into Calibre, which does a great job of conserving links to images, etc.
This route can also have unsatisfactory results but, on the whole, I have found it to be the most reliable route to a satisfactory epub.