By specification the widget annotation and its content can be merged into the field dictionary. When merged widget with Kids property is imported an InvalidCastException: 'Unable to cast object of type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Annotations.WidgetObject' to type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Forms.FormFieldNode'.' is thrown.