protected void convertToPdfButton_Click(object sender, EventArgs e)
{
    // Create a HTML to PDF converter object with default settings
    HtmlToPdfConverter htmlToPdfConverter = new HtmlToPdfConverter();

    // Set license key received after purchase to use the converter in licensed mode
    // Leave it not set to use the converter in demo mode
    htmlToPdfConverter.LicenseKey = "fvDh8eDx4fHg4P/h8eLg/+Dj/+jo6Og=";

    // Set an adddional delay in seconds to wait for JavaScript or AJAX calls after page load completed
    // Set this property to 0 if you don't need to wait for such asynchcronous operations to finish
    htmlToPdfConverter.ConversionDelay = 2;

    Document pdfDocument = null;
    try
    {
        string htmlWithDigitalSignatureMarker = htmlStringTextBox.Text;
        string baseUrl = baseUrlTextBox.Text;

        // Convert a HTML string with a marker for digital signature to a PDF document object
        pdfDocument = htmlToPdfConverter.ConvertHtmlToPdfDocumentObject(htmlWithDigitalSignatureMarker, baseUrl);

        // Make the HTML element with 'digital_signature_element' mapping ID a link to digital signature properties
        HtmlElementMapping digitalSignatureMapping = htmlToPdfConverter.HtmlElementsMappingOptions.HtmlElementsMappingResult.GetElementByMappingId("digital_signature_element");
        if (digitalSignatureMapping != null)
        {
            PdfPage digitalSignaturePage = digitalSignatureMapping.PdfRectangles[0].PdfPage;
            RectangleF digitalSignatureRectangle = digitalSignatureMapping.PdfRectangles[0].Rectangle;

            string certificateFilePath = Server.MapPath("~/DemoAppFiles/Input/Certificates/wnvpdf.pfx");

            // Get the certificate from password protected PFX file
            DigitalCertificatesCollection certificates = DigitalCertificatesStore.GetCertificates(certificateFilePath, "wnvpdf");
            DigitalCertificate certificate = certificates[0];

            // Create the digital signature
            DigitalSignatureElement signature = new DigitalSignatureElement(digitalSignatureRectangle, certificate);
            signature.Reason = "Protect the document from unwanted changes";
            signature.ContactInfo = "The contact email is support@winnovative-software.com";  
            signature.Location = "Development server";
            digitalSignaturePage.AddElement(signature);
        }

        // Save the PDF document in a memory buffer
        byte[] outPdfBuffer = pdfDocument.Save();

        // Send the PDF as response to browser

        // Set response content type
        Response.AddHeader("Content-Type", "application/pdf");

        // Instruct the browser to open the PDF file as an attachment or inline
        Response.AddHeader("Content-Disposition", String.Format("attachment; filename=Digital_Signatures.pdf; size={0}", outPdfBuffer.Length.ToString()));

        // Write the PDF document buffer to HTTP response
        Response.BinaryWrite(outPdfBuffer);

        // End the HTTP response and stop the current page processing
        Response.End();
    }
    finally
    {
        // Close the PDF document
        if (pdfDocument != null)
            pdfDocument.Close();
    }
}