Calibre will do this pretty well. The problem is that converting PDF to any ebook format is pretty awful, so pretty well is relative. Your output will be full of. weird stuff around page breaks (running heads and folios creeping in) hyphenation errors knackered chapter and scene breaks knackered fonts and styles broken structure (tables of contents links, etc) It won’t be a particularly clean or well-engineered epub, is the thing. If I ever need to do this - and I have, now and again - I use Calibre to convert it to RTF format in Microsoft Word first, then use find-and-replaces and spellcheck and things to tidy it up until it’s fairly reasonable and logical; then convert to EPUB from there.
You could then have the original Preformatted PDF's built up and saved into the appropriate library of PDFs you already have on your computer. So you only need to have the original PDF and the K2pdfopt would handle the rest. You will need to create a separate library for these PDFs however. If you do not already have one, then you can create one right now by following these simple steps: Download and install the Contact PDF viewer. This can be done from the Windows Control Panel Click on the Tools tab and select PDF Library under the File menu. Click on the “Edit” tab and add the correct libraries. Once this is complete, you can click on the Preformatted tab and import all of your PDF files into this library. This process generally takes only a few minutes.