Works fine for me, always has. Try deleting it and reinstalling it. If that doesn't work and it really bothers you, next step is probably to restore your phone.
So I have nailed it down to adding pictures, if I try and add a picture to a document or open a document with pictures in it it crashes. Has anyone else noticed this?
Apple's apps are sometimes designed to crash periodically if it recognizes that your device is jailbroken. I experienced this when using iBooks. Restored as new and it fixed itself.