If the document contains signature acrofields (or tags), it is possible to define which signature acrofields should be available for each and every signature Request. With multiple signatories, users
won’t sign where they shouldn’t or overlook signature fields.
Note: OTP signature requires signature acrofield
Read more about this functionality in 2.2 Create signature Request and chapters in examples describing multi-round signing 5.4 Multi-round signing with PDF with tags, 5.6 Multi-round signing with PDF with signature acrofields (specifically AllowedFields: SIGNATURE).