I've got it, but it's unreadable in my Cybook

I don't know if it's the font type, but it's too faded in my screen to be readable (and being in PDF, I can't even change the size of the font, to compensate).
I've tried to convert it to mobi, but then the formating get's awful (long sentences are broken, so you have a full line followed by a line with the 2 or three remaining words).
Here's how it looks in my Cybook (more or less), when converted to mobi (in PDF form, it just remains faded, the font is smaller, but the formatation is correct):