In the digital signature only mode, existing signatures will be preserved unless you called ISignature.Delete. But you can only sign existing signature lines, add invisible signatures, remove digital signature of signed signature lines, or remove invisible signatures in this mode. Other changes will be discarded.

After modifying digital signatures, you need to save the workbook to commit changes.

True to open workbook in digital signature only mode. Otherwise, use normal mode. The default value is False.