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In this demo you can learn how to add a digital signature to a PDF document based on a certificate from a PFX file. The digital signature is applied over an image in PDF document and you can click on that image to see the digital certificate properties.
Server Settings
IP: Port: Password:
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C# Code
using System;
using System.Collections.Generic;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using HiQPdfClient;

namespace HiQPdf_Demo
    public partial class DigitalSignatures : System.Web.UI.Page
        protected void buttonCreatePdf_Click(object sender, EventArgs e)
            string serverIP = textBoxServerIP.Text;
            uint serverPort = uint.Parse(textBoxServerPort.Text);
            string serverPassword = textBoxServerPassword.Text;

            // create a PDF document
            PdfDocument document = new PdfDocument(serverIP, serverPort);

            // use server password if necessary
            if (serverPassword.Length > 0)
                document.ServerPassword = serverPassword;

            // set a demo serial number
            document.SerialNumber = "YCgJMTAE-BiwJAhIB-EhlWTlBA-UEBRQFBA-U1FOUVJO-WVlZWQ==";

            // create a page in document
            PdfPage page1 = document.AddPage();

            // create the true type fonts that can be used in document text
            PdfFont pdfFontEmbed = document.CreateFontFromName("Times New Roman", 10, true);

            float crtYPos = 20;
            float crtXPos = 5;

            // add a title to PDF document
            PdfText titleTextTransImage = new PdfText(crtXPos, crtYPos,
                    "Click the image below to open the digital signature", pdfFontEmbed);
            titleTextTransImage.ForeColor = PdfColor.Navy;

            crtYPos += pdfFontEmbed.Size + 10;

            // layout a PNG image with alpha transparency
            PdfImage transparentPdfImage = new PdfImage(crtXPos, crtYPos, Server.MapPath("~") + @"\DemoFiles\Images\HiQPdfLogo_small.png");

            // apply a digital sgnature over the image
            PdfDigitalSignature digitalSignature = new PdfDigitalSignature(Server.MapPath("~") + @"\DemoFiles\Pfx\hiqpdf.pfx", "hiqpdf", 0);
            digitalSignature.SigningReason = "My signing reason";
            digitalSignature.SigningLocation = "My signing location";
            digitalSignature.SignerContactInfo = "My contact info";

                // write the PDF document to a memory buffer
                byte[] pdfBuffer = document.WriteToMemory();

                // inform the browser about the binary data format
                HttpContext.Current.Response.AddHeader("Content-Type", "application/pdf");

                // let the browser know how to open the PDF document and the file name
                HttpContext.Current.Response.AddHeader("Content-Disposition", String.Format("attachment; filename=DigitalSignatures.pdf; size={0}",

                // write the PDF buffer to HTTP response

                // call End() method of HTTP response to stop ASP.NET page processing

        protected void Page_Load(object sender, EventArgs e)
            if (!IsPostBack)