Gets or sets the creditor payment reference. The reference is mandatory for SwissQR IBANs i.e. IBANs in the range CHxx30000xxxxxx through CHxx31999xxxxx. If specified the reference must be either a valid SwissQR reference corresponding to ISR reference form or a valid creditor reference according to ISO 11649 RFxxxx. Both may contain spaces for formatting....class SwissQR namespace GroupDocs.Signature.Domain.Extensions assembly...assembly GroupDocs.Signature Debtor UnstructuredMessage...