Can we have a third sign off for Performance Document?

Summary: We have a case where employee does the self evaluation and sign's off the document and then Manager does the evaluation and Sign Off. Can we also have Participant Sign Off in our case the Director HR to sign?

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How to set a third signatory for the Performance Document, that is can we also have "Participant Sign Off" in our case the Director HR is a Participant and we want him to sign as well.

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