pdf's seem plenty readable (and my eyesight isn't the greatest), and that's with the DropBox app; not exactly a feature-rich pdf viewer. But my main concern was font size.
Regards,
Tom
On previous 7" tablets I found them unusable - too small. Using GoodReader on my new Mini, they are just large enough to be comfortable to read. The extra inch made a world of difference. Definitely love the new Mini.