Note the PRS-505 reader scales down the PDF to fit on the screen. So if the PDF is designed for the PRS-505 then they read just fine and work great. Howerver most PDF are created for printout 8.5x11 they will look tiny on the Reader, next to unreadable.
Most of us use PDFLRF a tool that turns the PDF to an image, then bolds the text and crops out the white spaces. Ths makes the PDFs very readable.
I've ran your PDF on PDFLRF and the output is very readable. (Note not the stand alone PDF)
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