Protected Sub convertToPdfButton_Click(ByVal sender As Object, ByVal e As EventArgs)
    ' Create a PDF document
    Dim pdfDocument As New Document()

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

    ' Add a page to PDF document
    Dim pdfPage As PdfPage = pdfDocument.AddPage()

    Try
        Dim htmlWithDigitalSignatureMarker As String = htmlStringTextBox.Text
        Dim baseUrl As String = baseUrlTextBox.Text

        ' Add a HTML string with a marker for digital signature to PDF document
        Dim htmlToPdfElement As New HtmlToPdfElement(htmlWithDigitalSignatureMarker, baseUrl)
        pdfPage.AddElement(htmlToPdfElement)

        ' Make the HTML element with 'digital_signature_element' mapping ID a link to digital signature properties
        Dim digitalSignatureMapping As HtmlElementMapping = htmlToPdfElement.HtmlElementsMappingOptions.HtmlElementsMappingResult.GetElementByMappingId("digital_signature_element")
        If digitalSignatureMapping IsNot Nothing Then
            Dim digitalSignaturePage As PdfPage = digitalSignatureMapping.PdfRectangles(0).PdfPage
            Dim digitalSignatureRectangle As RectangleF = digitalSignatureMapping.PdfRectangles(0).Rectangle

            Dim certificateFilePath As String = Server.MapPath("~/DemoAppFiles/Input/Certificates/wnvpdf.pfx")

            ' Get the certificate from password protected PFX file
            Dim certificates As DigitalCertificatesCollection = DigitalCertificatesStore.GetCertificates(certificateFilePath, "wnvpdf")
            Dim certificate As DigitalCertificate = certificates(0)

            ' Create the digital signature
            Dim signature As 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)
        End If

        ' Save the PDF document in a memory buffer
        Dim outPdfBuffer() As Byte = 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
        pdfDocument.Close()
    End Try
End Sub