It looks like a font problem where the PDF is using a specific font that for some reason can't be used on the two ereaders but can be used on your computer.
Two possible reasons that this could happen:
- PDF specifies a font that is not embedded. The computer has the font or has a very very close substitute while the ereaders don't have either the specified font or a reasonable substitute. Their substitute has different character spacing and lacks some of the glyphs.
- PDF specifies a font that is embedded. The computer can access the embedded font but the ereaders can't and are forced to fall back on a substitue font that is a very poor match and is missing needed glyphs.
Either way, it is unlikely that you will be able to tweak the ereaders to do a better job with the file, at least in its current state. It may be possible to create a file that the readers find more to their taste by opening the PDF on you computer in an app that can resave a new PDF with options for handling the font differently; options like embedding all fonts, converting fonts to outlines, rendering all pages as bitmaps, ... .