Reading FDF (Form Data Format) file in Flutter

Question

I have an FDF file (along with the PDF version of it), I'm following the documentation :

//Loads an existing PDF document.
final PdfDocument document =
    PdfDocument(inputBytes: File('input.pdf').readAsBytesSync());

//Import the FDF into the existing form.
document.form
  .importData(File('Import.fdf').readAsBytesSync(), DataFormat.fdf);

//Save the PDF document.
File('output.pdf').writeAsBytesSync(await document.save());

I'm getting this error:

E/flutter ( 8489): [ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Invalid argument(s): Incorrect field name.
E/flutter ( 8489): #0      PdfForm._importDataFDF.<anonymous closure> (package:syncfusion_flutter_pdf/src/pdf/implementation/forms/pdf_form.dart:353:11)
E/flutter ( 8489): #1      _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:633:13)
E/flutter ( 8489): #2      PdfForm._importDataFDF (package:syncfusion_flutter_pdf/src/pdf/implementation/forms/pdf_form.dart:348:11)

Any help/guidance on how to fix this?