Hi,
I just got my Sony PRS-505 and I'm really fascinated by this device.
Only problem is with PDF files where the font is so tiny that reading is difficult. And with magnification, the usual line formatting problems occur.
I have now found a free software for Mac OS that can crop the margins of PDF files which are then much more readable:
http://skim-app.sourceforge.net/
Maybe it helps you too.
Regards,
Juergen