Well, it depends on prices in your country...
GSMArena made a pretty good comparison between popular tablets: just search "GSMArena tablet shopping guide"
(I'm not allowed to post external links)
To my opinion, if your main purpose is to read a pdf files, and you don't mind a not-so-slick look and feel,
i would definitely recommend the nexus10 over other tablest in the mixture of price (especially if you can buy it thru Google Play Market), performance, screen and future update (official or by xda dev).
I don't know what would the nexus10 2 feature over the prev model, but be advised that it would cost much higher
(again- if GMarket is not available).