I use my Nook Color (running CM7 from the SD card) for color PDF documents. I'm basically using it as an Android tablet. I use QuickOffice from the Google Market, and it has really clean pan and zoom functions. The only downside is that it doesn't have bookmarking capabilities, so you always have to remember what page you were on. It has very good quality, overall, for color PDFs.
If you want a non-color eInk device, I just bought a Sony PRS 950 ($200 at Best Buy, if you can find one or buy the floor model) strictly for PDF reading. Of all the eInk readers I've tried, it has the best PDF support. The 7" screen means that you're already starting out on a good foot for PDF pages, and the reader has a LOT of custom zoom functions that you can then "lock" into place for the rest of the book once you find the right zoom "sweet spot" for that particular document.
I highly recommend the Sony PRS 950 for PDF reading, but keep in mind that you won't get color on it -- on the other hand, the battery life is great and you can read it in full sunlight, so that's a big plus.
Good luck, and feel free to PM me with any questions.
EDIT: Also, just adding: the Nook Color and PRS 950 do support landscape reading for PDFs; the new Nook 2 as far as I understand, does
not.