Kobo Vox is a 7" Android reader tablet, is $179.99 (in canada) and marketed as being optimized for reading outdoors contrary to most tablets. Since you want cheap, pdf and to read outdoors, it's probably your best choice. You can add the Ezpdf or Aldiko or Mantano reading apps to read your pdf material.
Quote:
1. Display
Both Kindle Fire and Kobo Vox sport 7-inch multitouch color displays. Amazon has deployed IPS (in-plane switching) technology and anti-reflective treatment on Kindle Fire’s display that offers a resolution of 1024 x 600 pixels at 169 ppi. Meanwhile, Kobo Vox’s display features a better resolution of 1024 x 800 pixels. Thanks to AFFS+ technology, the display of Vox has extra wide viewing angles and is optimized for reading in sunlight.
Winner: Kobo Vox as it has better screen resolution and AFFS+ technology.
Full article here:
http://www.gizmowatch.com/entry/earl...n-kindle-fire/
PS contrary to what the article says, you can add a micro-sd card to the Vox to expand it's memory beyond the tablet's own 8 gb.