The MediaBox defines the boundaries of the physical medium on
which the page may be displayed or printed. This may include bleed
areas or printing marks and also parts of the medium on which
printing cannot take place because of physicsal limitations of the
output technology. Any PDF drawing outside the MediaBox can be
These boundaries may be defined directly on the Page object or
they may be inherited from a parent Pages object.
A MediaBox is mandatory for all pages so this property should
never be null.
Assigning a new value to this property will change the property
for the current Page rather than any Pages object from which the
value may have been inherited. In this way the property exhibits a
Attempting to assign a null value to this property will result
in a NullReferenceException being thrown.