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.
Send approved partnership agreements to their signers.
Your signers receive the partner agreement after final approval, and you see their invitation links beside the approval.
Send approved new-client agreements to the named signer.
Your client gets the agreement to sign, and you get the request link and send confirmation on the project.