Signer Uploading Documents

Hello,

This is a very dumb question,but based on configuration and setting screens within OneSpan Sign, it reads as though the Signer has the ability to upload documents into the bundle. I know that the sender has the ability obviously along with creating the boxes/etc, but we're looking to see if there is something where once the bundle is sent to the signer, that the signer can upload say a PDF/word document to attach with the bundle.

Am I missing something?