Google Contacts, the address book built into Gmail, lets you keep track of all your contacts, see when you last interacted with them, and more.
File signed client agreements with their audit pages in client files.
Your final agreement folder holds the signed PDF and its audit certificate, and the owner gets links to both.
Send approved matter agreements for signature and return signer links.
Your signers get personal signature requests from the final agreement you email, and you get a reply with the invitation wording and their links.