documents

I'm looking for the best app for signing pdf documents while I'm on the go. There are several in the App Store but they're all paid apps. Which app lets me open a pdf from my email and lets me sign it either with my finger or a stylus and then email it back?

Are there any apps that let me send faxes from my iPad? These days I usually send all my signed documents via email but some clients insist that I send a fax. I need some app recommendations please as I refuse to to waste my time at Fedex sending a 3 fax.

Sure the iPad is full of apps for fun & games but what apps are available for business people who want to stay productive while commuting and such?