gspec, you don't tell us where you are located. That would help us make recommendations.
I very much like my jetBook Lite
, which has PDF reflow, so your PDF's would not be a problem. It has a built-in English dictionary which in my view is better suited for someone like yourself for whom English is a second language than it is for those of us for whom English is our native tongue.
It uses four AA flashlight batteries. We all buy eight rechargeables and a charger. Then we always have a set charged and ready to go when the current set runs down (which is about once every two weeks for many of us).
The screen is a reflective TFT screen, which means that the text is blacker than that of the eInk pearl screen. It's like looking at your wristwatch. No eye fatigue.
The jetBook Lite reads both mobi and ePub, and many other formats including rtf and fb2.
It is currently on sale at Newegg.com for $56.95.