If you want to read on iPad in the sun you should buy some good anti-glare screen protector but also buy or make yourself sunshade like these
http://www.youtube.com/watch?v=jiV2FaPw44c
http://www.youtube.com/watch?v=c6f8c6sd_AA
If you want good and cheaper 10" e-ink pdf reader you should buy used kindle dx and install kindlepdfviewer thereon.
https://www.mobileread.com/forums/sho...d.php?t=157047
If you also want to make handwritten notes in pdf's then you can do that in iPad or even some other e-ink reader (with stylus) while reading on kindle dx or buy yourself M92/Icarus Excel.