FDFDoc is a class representing Forms Data Format (FDF) documents. FDF is typically used when submitting form data to a server, receiving the response, and incorporating it into the interactive form. It can also be used to export form data to stand-alone files that can be stored, transmitted electronically, and imported back into the corresponding PDF interactive form. In addition, beginning in PDF 1.3, FDF can be used to define a container for annotations that are separate from the PDF document to which they apply.
FDFFieldIterator is an iterator type used to traverse interactive form fields
in a FDF document. A FDFFieldIterator points to FDF.FDFField nodes or to the