Have you looked into getting an enTourage eDGe? The full-sized model has a 9.7" e-ink screen and it is supposed to handle pdfs very well. The table of contents appears on the LCD screen for navigation (it is a "dualbook"), and the e-ink side is where you annotate.
I usually read epubs, so my personal experience is limited, but you might want to read user posts in these 2 forums:
http://www.entourageedge.com/forums/forum.php
https://www.mobileread.com/forums/forumdisplay.php?f=218
You'll see the company is having difficulties, but they haven't folded. And if you are worried they might, you can buy an extended warranty from some of the retailers.
Anyway, it's worth a look, as long as you're researching -- and it might be just what you want!
Happy hunting!!