Add Watermarks and Stamps to Generated PDF Document

protected void convertToPdf()
{
    // Get the server IP and port
    String serverIP = textBoxServerIP.Text;
    uint serverPort = uint.Parse(textBoxServerPort.Text);

    // Create a HTML to PDF converter object
    HtmlToPdfConverter htmlToPdfConverter = null;
    if (radioButtonUseTcpService.Checked)
        htmlToPdfConverter = new HtmlToPdfConverter(serverIP, serverPort);
    else
        htmlToPdfConverter = new HtmlToPdfConverter(true, textBoxWebServiceUrl.Text);

    // Set optional service password
    if (textBoxServicePassword.Text.Length > 0)
        htmlToPdfConverter.ServicePassword = textBoxServicePassword.Text;

    // 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 = "4W9+bn19bn5ue2B+bn1/YH98YHd3d3c=";

    // 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;

    // Convert a HTML page to a PDF document object
    Document pdfDocument = htmlToPdfConverter.ConvertUrlToPdfDocumentObject(urlTextBox.Text);

    // Get the stamp width and height
    float stampWidth = float.Parse(stampWidthTextBox.Text);
    float stampHeight = float.Parse(stampHeightTextBox.Text);

    // Center the stamp at the top of PDF page
    float stampXLocation = (pdfDocument.GetPage(0).PageSize.Width - stampWidth) / 2;
    float stampYLocation = 0;

    // Create the stamp template to be repeated in each PDF page
    Template stampTemplate = pdfDocument.AddTemplate(stampXLocation, stampYLocation, stampWidth, stampHeight);

    // Create the HTML element to add in stamp template
    HtmlToPdfElement stampHtmlElement = new HtmlToPdfElement(htmlStringTextBox.Text, baseUrlTextBox.Text);

    // Set the HTML viewer width for the HTML added in stamp
    stampHtmlElement.HtmlViewerWidth = 600;
    // Fit the HTML content in stamp template
    stampHtmlElement.FitWidth = true;
    stampHtmlElement.FitHeight = true;

    // Add HTML to stamp template
    stampTemplate.AddElement(stampHtmlElement);

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