To each his own, but I've given up on using e-ink readers for pdf's. I either convert and tweak them or I read them on my 9" Nook HD+, which remains the least expensive, large-screen HD android tablet, particularly if you buy a used or refurb. For ecample, here are the current offers for the HD+ 32GB in the Amazon marketplace:
http://www.amazon.com/gp/offer-listi...&condition=all
Of the current offers, Ocean Reef Electronics would be my choice. Their price is great ($99 + $12.49 shipping) and they're a reputable seller that I've done business with several times. For the price difference, I definitely recommend the 32GB over the 16GB.