To provide a little more context, I am also not able to get the form fields when posting to an ASP.NET web form. Here's my code:
MergeDocument document = new MergeDocument(MapPath("PurchaseOrderReport.pdf"));
Label sigLabel = new Label("Enter Initials and Click Approve", 50, 0, 180, 20) { Font = Font.Helvetica, FontSize = 9 };
TextField iniField = new TextField("InitialText", 50, 25, 150, 20) { BorderStyle = BorderStyle.Solid };
Button submitButton = new Button("submitButton", 50, 50, 70, 25) { Label = "Approve" };
TextField resLabel = new TextField("result", 120, 50, 100, 25)
{
Font = Font.Helvetica,
FontSize = 9
};
SubmitAction action = new SubmitAction("http://localhost:63475/Approve.aspx", FormExportFormat.HtmlPost);
submitButton.Action = action;
AnchorGroup anchorGroup = new AnchorGroup(200, 80, Align.Center, VAlign.Bottom);
anchorGroup.Add(sigLabel);
anchorGroup.Add(iniField);
anchorGroup.Add(submitButton);
anchorGroup.Add(resLabel);
Page page = document.Pages[document.Pages.Count - 1];
page.Elements.Add(anchorGroup);
document.DrawToWeb("SubmitTest.pdf");