Free. Current App Store rating: 4.5 stars
You're traveling, and your signature on an important doc is needed asap. If possible, you can use the cool PDF document signature-signing feature in Apple's Preview app for OS X. If you're traveling with your iPad you need SignNow. The iPhone/iPad app lets you sign PDF, Word and RTF documents with a finger. The documents can come via email or an iOS device camera, Dropbox or other sources. When you're done, email the signed document or save it to your SignNow account. Heads up: The free version limits you to signing five docs per month, which is probably enough. Otherwise, you'll need to pay for SignNow Pro ($15 or $25 per month).