Open a document within your browser locally through the extension or on the web (like this).
Click on the chrome extension/
Then create a document name (it will default to the file name), click 'add additional signer,' add the signer's email, and press enter. Repeat the process to add additional signers.
You are then able to sign the document or send without signing. If you select 'send without signing' you will still be able to sign the document at a later time.