private void btnConvertToHtml_Click(object sender, EventArgs e)
{
    if (pdfFileTextBox.Text.Trim().Equals(String.Empty))
    {
        MessageBox.Show("Please choose a source PDF file", "Choose PDF file", MessageBoxButtons.OK);
        return;
    }

    // the source pdf file
    string pdfFileName = pdfFileTextBox.Text.Trim();

    // start page number
    int startPageNumber = int.Parse(textBoxStartPage.Text.Trim());
    // end page number
    // when it is 0 the conversion will continue up to the end of document
    int endPageNumber = 0;
    if (textBoxEndPage.Text.Trim() != String.Empty)
        endPageNumber = int.Parse(textBoxEndPage.Text.Trim());

    // create the converter object and set the user options
    PdfToHtmlConverter pdfToHtmlConverter = new PdfToHtmlConverter();

    pdfToHtmlConverter.LicenseKey = "UtzN3cnM3c3dy9PN3c7M08zP08TExMTdzQ==";

    // set the resolution of HTML images
    pdfToHtmlConverter.Resolution = int.Parse(textBoxResolution.Text);

    // set the zoom of HTML content
    pdfToHtmlConverter.Zoom = int.Parse(textBoxZoom.Text);

    // the demo output directory
    string outputDirectory = Path.Combine(Application.StartupPath, @"DemoFiles\Output");

    Cursor = Cursors.WaitCursor;
            
    try
    {
        // convert PDF pages to HTML files in a directory
        pdfToHtmlConverter.CreateIndexFile = true;
        pdfToHtmlConverter.ConvertPdfPagesToHtmlFile(pdfFileName, startPageNumber, endPageNumber, outputDirectory, "PdfPage");

        // uncomment the lines below to raise the PageConvertedEvent event when a PDF page is converted
        // the pdfToHtmlConverter_PageConvertedEvent handler below will be executed for each converted PDF page
        // Do not forget to uninstall the handler when is not needed anymore
        //pdfToHtmlConverter.PageConvertedEvent += pdfToHtmlConverter_PageConvertedEvent;
        //pdfToHtmlConverter.ConvertPdfPagesToHtmlInEvent(pdfFileName, startPageNumber, endPageNumber);

        // uncomment the line below to convert PDF pages in memory to an array of PdfPageHtml objects
        //PdfPageHtml[] pdfPageHtmls = pdfToHtmlConverter.ConvertPdfPagesToHtml(pdfFileName, startPageNumber, endPageNumber);
    }
    catch (Exception ex)
    {
        // The conversion failed
        MessageBox.Show(String.Format("An error occurred. {0}", ex.Message), "Error");
        return;
    }
    finally
    {
        Cursor = Cursors.Arrow;
    }

    try
    {
        System.Diagnostics.Process.Start(outputDirectory);
    }
    catch (Exception ex)
    {
        MessageBox.Show(string.Format("Cannot open output folder. {0}", ex.Message));
        return;
    }
}

/// <summary>
/// The PageConvertedEvent event handler called after when a PDF page was converted to HTML
/// The event is raised when the ConvertPdfPagesToHtmlInEvent() method is used
/// </summary>
/// <param name="args">The handler argument containing the PDF page HTML and page number</param>
void pdfToHtmlConverter_PageConvertedEvent(PageConvertedEventArgs args)
{
    // get the HTML document and page number from even handler argument
    string  pdfPageHtml = args.PdfPageHtml.Html;
    int pageNumber = args.PdfPageHtml.PageNumber;

    // save the PDF page HTML to a file
    string outputHtmlFile = Path.Combine(Application.StartupPath, @"DemoFiles\Output", "PdfPage_" + pageNumber + ".html");
    File.WriteAllText(outputHtmlFile, pdfPageHtml, Encoding.UTF8);

    args.PdfPageHtml.Dispose();
}