PDFs are not really made to be converted. PDF was designed as an output format, not an input format.
Also, you seem to want to have your cake and eat it too. If the reason you don't like just to read the PDFs as is is that the layout is not right, you can't both preserve that format AND convert to something that doesn't have that layout.
However, my best advice would be to keep the file in PDF format and process with
soPDF first. The results won't be perfect, but generally, this helps make things much easier to read in a small screen will preserving the look of the PDF exactly.