// Controls if the current HTML page will be rendered to PDF or as a normal page
bool convertToPdf = false;

protected void convertToPdfButton_Click(object sender, EventArgs e)
{
    // The current ASP.NET page will be rendered to PDF when its Render method will be called by framework
    convertToPdf = true;
}

protected override void Render(HtmlTextWriter writer)
{
    if (convertToPdf)
    {
        // Get the current page HTML string by rendering into a TextWriter object
        TextWriter outTextWriter = new StringWriter();
        HtmlTextWriter outHtmlTextWriter = new HtmlTextWriter(outTextWriter);
        base.Render(outHtmlTextWriter);

        // Obtain the current page HTML string
        string currentPageHtmlString = outTextWriter.ToString();

        // 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;
                
        // Use the current page URL as base URL
        string baseUrl = HttpContext.Current.Request.Url.AbsoluteUri;

        // Convert the current page HTML string a PDF document in a memory buffer
        byte[] outPdfBuffer = htmlToPdfConverter.ConvertHtml(currentPageHtmlString, baseUrl);

        // 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=Convert_Current_Page.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();
    }
    else
    {
        base.Render(writer);
    }
}