Originally Posted by FunkeXMix
I would really appreciate if you could give me an estimate for how long it takes to convert a PDF to a fully functioning Epub file?
Like DaleDe said. It depends on how the PDF was made, and what you're using to convert it.
PDF is less a "filetype" and more a wrapper for content that can be viewed on many different machines. It was designed to be printable--everything else came later, and support for "convert *away* from PDF" is erratic. If the PDF was made from an XHTML file with conversion in mind, switching to something else is relatively easy. If the PDF was made from an older version of Word, then every line break may be a hard return, and take extensive time to convert to useful ebook formats. If the PDF is scanned images, they'll need to be OCR'd & corrected first--and those images might look fine on the screen but still be low-resolution enough to cause swarms of OCR errors.
For a lot of commercially-released PDFs, usually exported from InDesign or Word, conversion to epub can be as little as an hour or two--if you're comfortable with all the steps, and willing to accept a few formatting errors (like extra paragraph or page breaks). If not, then you need a page-by-page check, possibly a line-by-line check, and how long that takes depends on your reading speed and familiarity with the program(s) you're using.