In some cases, you need approval and delivery confirmation for a participant, but not a signature. In those cases, you can easily send for approval only.
To send a document for approval, upload your document(s) and add your participants as normal but do not place any signature fields for the customer that only needs to approve. Then send the document for signing. Any participant without signature fields will get the normal email but it will say "Please APPROVE..." instead of sign.
The participant will review the document and there will be an Approve button instead of a Sign button. The audit trail and security are the same as with e-Signed documents.