For HTML2PDF and XML2PDF solution check our PDFDoc Scout ActiveX library instead

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using Bytescout.PDF;

namespace DigitalSignature
{
class Program
{
static void Main(string[] args)
{
// Create main PDF Doc Engine
PDFDocEngine engine = new PDFDocEngine("demo", "demo");

// Open existing document
Document document = engine.AddDocument("HelloWorld.pdf");

// add digital signature from file
document.AddSignature("dig-signature.pfx", "John Doe", "Approved", false, "123456");

// now add visible signature drawing
Rectangle R;
R.Left = 10;
R.Top = 10;
R.Right = 800;
R.Bottom = 300;
// add signature for the rectangle
// IMPORTANT NOTE: Y scale of the rectangle is inverted due to the PDF nature ( 0,0 point in PDF starts at left bottom corner)
Drawing SignatureDrawing = document.GetPage(0).AddVisibleSignature(R);

// Add standard font
uint font = document.AddFontStandard(StandardFontType.Courier, FontEncodingType.WinAnsi);

// Set Active Font
SignatureDrawing.SetActiveFont(font, 50, false, false);

// draw a text
SignatureDrawing.PlaceText(10, 10, 0, "Approved by John Doe");
SignatureDrawing.Close();

// Save document
document.Save("signedWithVisibleSignature.pdf");

// open generated PDF document in default PDF viewer installed in Windows
Process.Start("signedWithVisibleSignature.pdf");
}
}
}

Download example source code: bytescoutpdf_add_visible_digital_signature_to_pdf.zip (14 KB)

For HTML2PDF and XML2PDF solution check our PDFDoc Scout ActiveX library instead