The downside to eReaders is generally the small screen. You open up a PDF file and the fonts are smaller than you’d wish them to be. You can always zoom, but why not prepare your file from the beginning? If you have a CHM file and you want to convert it to a PDF to be later loaded on your eReader, try this:
chm2pdf –bottom margin5 –left margin5 –right margin5 –top margin5 –book filename.chm
This will trim the edges of the CHM file and convert the file to PDF.