bool fdf_set_ap (int fdf_document, string field_name, int face, string filename, int page_number)
The fdf_set_ap() function sets the
appearance of a field (i.e. the value of the /AP key).
The possible values of face
are 1=FDFNormalAP, 2=FDFRolloverAP, 3=FDFDownAP.
