While working at tech startups, Abe Geiger saw an opportunity to make the handling of contracts between freelancers and the businesses who hire them as easy as a handshake.

The result of that idea is Shake, an app that simplifies the process of creating, signing, and managing legal contracts.

Through Shake, users can customize document templates, cutting out the need to hire a lawyer to write and supervise a legal agreement as well as the need to meet in person to sign contracts.

Since launching in 2012, the app, which can now also be used on any Internet device at Shakelaw.com, has been downloaded by hundreds of thousands of users.

With Shake Pro, which debuted earlier this month, Geiger is offering an upgrade to his app that adds even more business services.

The beefed-up version allows businesses to upload specific legal documents they need to use and keep them private in their account.

"[Shake Pro users] want the simplicity of the platform and they want to be able to make changes or get signatures on a mobile or desktop, but they have their own versions of their own forms," Geiger said.

Shake Pro has a monthly fee of $10 if you sign up for a year, or $15 per month.

The templates are free, but there is a fee to upload your own document.

Among its other features, Shake Pro identifies important dates -- such as when things are due or set to expire -- in contracts and notifies parties of upcoming deadlines via smartphone notifications.

Shake Pro users can also brand themselves by customizing the document with their business logo.

"If you're a small business and you're selling something, a good or service, we want to make it easy for you to get that contract done so you can get to work," said Geiger, whose company office is downtown on Mulberry Street. "Whether they need our contracts or have their own, we want to be able to support that."