Welcome to mobileread, gspec!
If you want it for reading PDF documents, don't get an e-reader - it's a horrible experience trying to read PDF on them. I think you would be better reading PDFs on a tablet, but as I don't have one, I hesitate to advise you on which one. You really need to go and look at them if you can and see how they work and which one you like. Or else just buy another iPad! However, a lot of people find the bright screen can be tiring to the eyes after a while, where the e-ink screens of ereaders is much easier on the eyes.
There are several good ereaders and again, it is really a case of trying them out if you can do so. It would probably be good for someone with experience of, say, a Kindle and a Kobo or Sony to comment on preferences here. There are certainly some problems with the latest firmware from Kobo, but that will be sorted out in time, and no doubt other ereaders have similar problems from time to time. However, there are plenty of people with the technical knowhow to give helpful advice if you are having problems with your ereader.
I certainly enjoy reading on my Kobo, and tend to alternate between it and paper books, depending on what I'm reading.
Good luck with whatever you decide to get, and enjoy reading on it.