While documents may be relied upon during evidence, a witness must be called to explain what those documents are. The Labour Court made this quite clear in the matter of Assmang Limited (Blackrock Mine) v De Beer and Others (JR948/14) [2017] ZALCJHB 78 (28 February 2017):

[8] Mr Markus appears to have pinned all of his hopes of proving that the dismissal had been fair on an
interpretation of the pre-placement medical form itself, but without leading any evidence to support his
interpretation of that form. It is trite that documents which a party seeks to rely on for the purpose of
legal proceedings, no matter how crucial or self-evident a document may seem to be, can only have
evidentiary value relevant to the extent to which they are contextualised by a witness who talks to the
document in question.