This class represents the pushbutton field dictionary. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; page 440.

This class is always an indirect object because it inherits from FieldElement which is always an indirect object.

System.Object
    WebSupergoo.ABCpdf13.Elements.Element
       WebSupergoo.ABCpdf13.Elements.FieldElement
          WebSupergoo.ABCpdf13.Elements.PushbuttonFieldElement