A submit-form action: sends the values of interactive form fields to a URL. The library never submits anything.
public sealed class PdfSubmitFormAction : PdfAction
ISO 32000-2 §12.7.6.2, Tables 239 and 240 (PDF 1.2). Table 239 marks Flags and CharSet "inheritable" without saying
from where; they are read from the action dictionary only.
kind:method, kind:property, kind:ctor. Press Esc to clear.CharacterSetGets the character set of the submitted data (CharSet, PDF 2.0), such as utf-8, or null.FieldsGets the fields to include or, with Exclude, exclude (Fields): field dictionaries and (PDF 1.3) fully qualified field names; null when absent: every field.FileGets the URL to submit to (F, required; a URL file specification, §7.11.5), or null.KindGets the type of action ActionType names in Table 201, or Unknown.