The Sender can check the progress of the document in the document detail view such as which party has signed and not. Just tap on the info icon in the document listing screen and you will be able to view the progress under Document Activity section. The sender will also be notified about via email and push notification once a signer signs and when all the parties have signed the requested document.

PS: Request Signature feature is available on app version v4.2.0 and higher, under Business plan.