I know sony reader prs-505 can switch language with firmware modification. You can search for the term "firmware" in the first review below and you’ll see:

http://www.amazon.com/gp/redirect.html?ie=UTF8&location=http%3A%2F%2Fwww.amazon.com%2Freview%2FB000WP2RC2%3Fie%3DUTF8%26ref%255F%3Ddp%255Ftop%255Fcm%255Fcr%255Facr%255Ftxt%26showViewpoints%3D1&tag=querystr-20&linkCode=ur2&camp=1789&creative=390957

For PDF support, sony reader is much better when compared to the Kindle. You can see opinion from this actual customer on Amazon below, it compares the Kindle 2 and the latest versions of sony readers:

http://www.amazon.com/gp/redirect.html?ie=UTF8&location=http%3A%2F%2Fwww.amazon.com%2Freview%2FR1CN3ORBH2I3F3%3Fie%3DUTF8%26ASIN%3DB001DZG604%26ref%255F%3Dcm%255Fcr%255Fpr%255Fcmt&tag=querystr-20&linkCode=ur2&camp=1789&creative=390957