It took a while for technology to catch up with the ESIGN act of 2000, but now that it has there's a whole bunch of apps available to make signing documents on mobile devices easier. DocuSign has long been a leader, and its mobile app might be a great fit if signing contracts is part of your daily life.
The average DocuSign user doesn't need to pay if they're just receiving documents. If you need to send them you can sign up for one of several packages available in the app. The cheapest is $14.99 a month (or $119.00 a year), which allows you to send up to 10 documents monthly.
Prices go up from the basic paid plan, but if you run a paperwork-heavy business it's a good investment.