We apologize for the delay in response to your query.
Looking at the description above, if you are willing to add your signature after getting the document signed by signer. The you simply place yourself (your email) last in the "Signing" order and your other signers first.
Following the steps suggested in the help document, when you place the signers email in 1st and 2nd place then add your email at the end and assign a signature field for yourself too. In this way once the other signer have signed the document it will route to you and then you can add your signature on the same document.
Hope this answers your query.
You can also do it by adding two signature fields, setting the first one to lock all other fields except for the second signature, when signed.