David Soulayrol is absolutely correct. The whole point of the PDF format is to allow the author/publisher, not the reader, to control the appearance of the document. It was designed to support typography properly. Think of it as a page sized image, designed to allow printers to duplicate the look of an original document.
Even html/epub/css does not have all the functions of PDF (or of real typography), and therefore, conversions involving graphics or tables will never be very successful.
If you don't like how PDF documents render on a device, get your material in another format more suitable for the device..