Documents can also be sent unsigned by way of approval.
If it’s not just one of the attachments that you want unsigned, but the entire document, then instead of removing signature fields for the given attachment, just use the Approves option, which is available for the whole document right when you are choosing the counterparties in the document header:
Each user will receive their notifications as usual, but instead of calling for a signature, the system will just call them to approve the document with a single click.