Any field of form is represented by a mandatory field data and optional annotation, which defines the visual appearance of field. The base class that defines the form field data is PdfInteractiveFormField. The base class that defines the annotation, which defines the appearance of from field, is PdfWidgetAnnotation. An instance of PdfInteractiveFormField class stores a link to corresponding instance of PdfWidgetAnnotation class in PdfInteractiveFormField.Annotation property.

The field may have some child fields, the list of child fields can be obtained using PdfInteractiveFormField.Kids property. The field without child fields is called a terminal field. The terminal field always has the annotation, which defines its appearance. Non-terminal field has no annotation.

A parent field for the current field can be obtained using PdfInteractiveFormField.Parent property.


The form field has a partial field name, which is stored in PdfInteractiveFormField.PartialName property and can be set. Also the form field has a full field name, which is stored in PdfInteractiveFormField.FullyQualifiedName property and cannot be set. The full name of form definitely identifies a field in form and is constructed from the partial field name and partial names of parent fields. The partial field name equals the full field name if the field has no parent fields. The parent field name cannot include a dot symbol.


The SDK supports the following field types:

• PdfInteractiveFormButtonField - a base class for fields which define push button, radio button, check box
  • PdfInteractiveFormCheckBoxField - a field defining a check box
  • PdfInteractiveFormPushButtonField - a field defining a push button
  • PdfInteractiveFormRadioButtonField - a field defining a radio button
  • PdfInteractiveFormRadioButtonGroupField - a field defining a group of radio buttons
• PdfInteractiveFormChoiceField - a field defining a combo box or list box
  • PdfInteractiveFormComboBoxField - a field defining a combo box
  • PdfInteractiveFormListBoxField - a field defining a list box
• PdfInteractiveFormSignatureField - a field that contains a digital signature
• PdfInteractiveFormTextField - a field defining a box or space in which the user can enter text from the keyboard
• PdfInteractiveFormBarcodeField - a field that contains a barcode

Please read how to work with PDF interactive form in the following articles:

• Get information about fields of PDF interactive form
• Extract field values from PDF interactive form
• Add field to the PDF interactive form
• Change field value in PDF interactive form
• Remove field from PDF interactive form
• Work with actions of PDF interactive form field
• Import and export data of PDF interactive form