Found it. It's in German though. The link is here:
http://www.ebookreadertests.de/vergleich-beste-ebook-reader-fur-pdf/
They are saying that the best e-reader for pdfs is the Kindle DX. They are also saying that that Kindle is available only from amazon.com. The reason as to why this Kindle is the best solution, they say, is because the screen is bigger than those of other e-readers and a whole pdf page can be displayed (no scrolling necessary) with the font remaining legible (even small font sizes).
The problem with many other e-readers is that their displays are too small and you will have to scroll up and down, left and right, in order to view the whole page. Very annoying, as I have a pdf on my Kindle Paperwhite and it is precisely what I have to do.
The article also reads that the Kindle Touch is the second best e-reader for pdfs, and the Archos 70b Tablet being the third best. They are also saying, the normal Kindle is a cheap alternative because you can change the display to horizontal, i.e. you can view a whole page horizontally. However, when you do that with a page that has a small font, the text may not be legible simply because the display per se is too small, i.e. you'll have to end up scrolling.
Generally speaking, they are also saying getting a tablet PC could be a good thing for mainly reading pdfs (as they have bigger displays).
Hope this helps.