Google Drive is Google's file sync app that lets you store all of your files online alongside your Google Docs documents, and keep them synced with all of your devices.
Send matter owners links to signed agreements and signing proof.
Your signed settlement and retainer agreements reach the right matter folder, with signing certificates and links for the matter owner.
Send the approved client agreement and keep its signature request in view.
Your agreement goes to the right signers in the order you choose, and the case gives its owner a link to the request.