The default appearance (DA) used for the text.
The ArrayAtom is a sequence of PDF parameters and operators
which makes up a complete drawing sequence.
This property controls the base set of drawing instructions used
for controlling the appearance of variable text in a field. Getting
this property gets the effective value which may be inherited.
Setting this property sets the value on this item itself.
Similarly setting this property to null will remove the property
on the item itself but the value may continue to be inherited. The
appearance of the field is not updated until you change the
Value or call UpdateAppearance.