General - Converting PDF files to ePub

Hi,

Im trying to convert PDF files to ePub and looking for a good conversion library(or command line tool).

i have already tested known libraries - Aspose, Calibre, pdftohtml, pdf2html,MS Interop office 2010/2013 lib, etc ... trying to convert in several methods:

directly from PDF to ePub, PDF->HTML->ePub, PDF->RTF->ePub.

all tests failed with different reasons, mostly on table conversion, images and text indent.
tables are translated to raw text files and images disappear.

using MS Office 2013 interop library, i was able to get good but not perfect results, and since the library is not open source, i can't fix the flaws(mostly text indent)

it seems that the problem exists in the problematic PDF format and converting from editable source(such as RTF or DOC) seems to somehow work. most PDF conversion tools i found converts graphic elements(table fill colors, borders, etc) to images and sometimes even to one grouped image for each page and ePub can't handle it.
unfortunately, this is not the case and i have no way of getting the source documents(editable format), only the PDF versions.

is there any other known good PDF to ePub conversion method?

hope this topic fits the forum,
thanks