This is a software that helps you generate calibre style epub file from a given PDF file.
Download the build folder as a zip archive and open the "Epub Maker.exe" file and you'll be greeted with the window to select your PDF file and clicking on that button, you'll be able to select your PDF and get the epub file created right away with the same name.
It uses the calibre format for epub file creation and should be useful for publishing in platforms like ingramspark.