Protected Sub convertToPdfButton_Click(ByVal sender As Object, ByVal e As EventArgs)
    ' Create a HTML to PDF converter object with default settings
    Dim htmlToPdfConverter As 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="

    ' Select the HTML elements for which to retrieve location and other information from HTML document
    htmlToPdfConverter.HtmlElementsMappingOptions.HtmlElementSelectors = New String() {htmlElementsSelectorTextBox.Text}

    Dim pdfDocument As Document = Nothing
    Try
        ' Convert HTML page to a PDF document object which can be further modified to highlight the selected elements
        pdfDocument = htmlToPdfConverter.ConvertUrlToPdfDocumentObject(urlTextBox.Text)

        ' Highlight the selected elements in PDF with colored rectangles
        For Each htmlElementInfo As HtmlElementMapping In htmlToPdfConverter.HtmlElementsMappingOptions.HtmlElementsMappingResult
            ' Get other information about HTML element
            Dim htmlElementTagName As String = htmlElementInfo.HtmlElementTagName
            Dim htmlElementID As String = htmlElementInfo.HtmlElementId

            ' Hightlight the HTML element in PDF

            ' A HTML element can span over many PDF pages and therefore the mapping of the HTML element in PDF document consists 
            ' in a list of rectangles, one rectangle for each PDF page where this element was rendered
            For Each htmlElementLocationInPdf As HtmlElementPdfRectangle In htmlElementInfo.PdfRectangles
                ' Get the HTML element location in PDF page
                Dim htmlElementPdfPage As PdfPage = htmlElementLocationInPdf.PdfPage
                Dim htmlElementRectangleInPdfPage As RectangleF = htmlElementLocationInPdf.Rectangle

                ' Highlight the HTML element element with a colored rectangle in PDF
                Dim highlightRectangle As New RectangleElement(htmlElementRectangleInPdfPage.X, htmlElementRectangleInPdfPage.Y, htmlElementRectangleInPdfPage.Width, htmlElementRectangleInPdfPage.Height)

                If htmlElementTagName.ToLower() = "h1" Then
                    highlightRectangle.ForeColor = Color.Blue
                ElseIf htmlElementTagName.ToLower() = "h2" Then
                    highlightRectangle.ForeColor = Color.Green
                ElseIf htmlElementTagName.ToLower() = "h3" Then
                    highlightRectangle.ForeColor = Color.Red
                ElseIf htmlElementTagName.ToLower() = "h4" Then
                    highlightRectangle.ForeColor = Color.Yellow
                ElseIf htmlElementTagName.ToLower() = "h5" Then
                    highlightRectangle.ForeColor = Color.Indigo
                ElseIf htmlElementTagName.ToLower() = "h6" Then
                    highlightRectangle.ForeColor = Color.Orange
                Else
                    highlightRectangle.ForeColor = Color.Navy
                End If

                highlightRectangle.LineStyle.LineDashStyle = LineDashStyle.Solid

                htmlElementPdfPage.AddElement(highlightRectangle)
            Next htmlElementLocationInPdf
        Next htmlElementInfo

        ' 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=Select_in_API_HTML_Elements_to_Retrieve.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 IsNot Nothing Then
            pdfDocument.Close()
        End If
    End Try
End Sub