No need for a printer, scanner, fax machine--or even a pen--to sign and send important documents anymore. New apps for mobile devices let you create a clear signature with just your finger.

SignNow

This app for the iPhone, Android, and iPad lets you upload a Word document or PDF from your phone's e-mail, camera, or Dropbox account and tap to insert your signature. You can sign with your finger or upload a saved signature. Copies of signed documents can be sent by e-mail or saved in the cloud.
Cost: Free

DocuSign Ink

This free app for the iPhone, iPad, and Android devices is similar to SignNow but touts extra document encryption, authentication of signers' identities, and an audit trail showing who signed, when, and where. The paid version, called DocuSign, also lets you send documents to multiple parties and create e-mail reminders.
Cost: Paid version, $14.99 and up

Sign Here

This app lets you create commonly used legal and business documents right on your iPhone. Choose one of 15 document types"bill of sale, nondisclosure agreement, contract"answer a few questions to customize it, sign with your finger, and e-mail the finished document.
Cost: The app is free, but most documents cost 30 cents to $1.50 apiece.