This class represents the submit-form action. This is definitively detailed in:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 236, page 451.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 239, page 548.

System.Object
    WebSupergoo.ABCpdf14.Elements.Element
       WebSupergoo.ABCpdf14.Elements.ActionElement
          WebSupergoo.ABCpdf14.Elements.SubmitFormActionElement

A submit-form action sends form field values to a server-side URL. The F entry holds the URL. The Fields entry lists included or excluded fields. The Flags integer controls submission format (URL-encoded FDF, XFDF, HTML, or full PDF).

The CharSet entry (PDF 2.0) specifies the character encoding for submitted text data.