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

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

    // the output text layout
    TextLayout textLayout = SelectedTextLayout();

    // the output text encoding
    System.Text.Encoding textEncoding = SelectedTextEncoding();

    // page breaks
    bool markPageBreaks = cbMarkPageBreaks.Checked;

    string outputFileName = System.IO.Path.Combine(Application.StartupPath, @"DemoFiles\Output", 
            System.IO.Path.GetFileNameWithoutExtension(pdfFileName) + ".txt");

    // create the converter object and set the user options
    PdfToTextConverter pdfToTextConverter = new PdfToTextConverter();

    pdfToTextConverter.LicenseKey = "C4WUhJaRhJSEkoqUhJeVipWWip2dnZ2ElA==";

    pdfToTextConverter.Layout = textLayout;
    pdfToTextConverter.MarkPageBreaks = markPageBreaks;

    Cursor = Cursors.WaitCursor;
    try
    {
        // extract text from PDF
        string extractedText = pdfToTextConverter.ConvertToText(pdfFileName, startPageNumber, endPageNumber);

        // write the resulted string into an output file 
        // in the application directory using the selected encoding
        System.IO.File.WriteAllText(outputFileName, extractedText, textEncoding);
    }
    catch (Exception ex)
    {
        MessageBox.Show(String.Format("An error occurred. {0}", ex.Message), "Error");
        return;
    }
    finally
    {
        Cursor = Cursors.Arrow;
    }


    try
    {
        System.Diagnostics.Process.Start(outputFileName);
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
        return;
    }
}

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

    if (textToFindTextBox.Text.Trim().Equals(String.Empty))
    {
        MessageBox.Show("Please enter the text to find", "Text to Find", MessageBoxButtons.OK);
        return;
    }

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

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

    Cursor = Cursors.WaitCursor;
    string outputFileName = System.IO.Path.Combine(Application.StartupPath, @"DemoFiles\Output",
            System.IO.Path.GetFileNameWithoutExtension(pdfFileName) + "_Highlighted.pdf");
    Document pdfDocument = null;
    try
    {
        // create the PDF to Text converter
        PdfToTextConverter pdfToTextConverter = new PdfToTextConverter();

        pdfToTextConverter.LicenseKey = "C4WUhJaRhJSEkoqUhJeVipWWip2dnZ2ElA==";

        // search text in PDF
        FindTextLocation[] findTextLocations = pdfToTextConverter.FindText(pdfFileName, textToFindTextBox.Text,
                    startPageNumber, endPageNumber, cbCaseSensitive.Checked, cbWholeWord.Checked);

        // open the PDF to search in PDF library
        pdfDocument = new Document(pdfFileName);

        // highlight the found text in PDF
        foreach (FindTextLocation findTextLocation in findTextLocations)
        {
            RectangleElement highlightRectangle = new RectangleElement(findTextLocation.X, findTextLocation.Y,
                findTextLocation.Width, findTextLocation.Height);
            highlightRectangle.BackColor = Color.Yellow;
            highlightRectangle.Opacity = 50;

            pdfDocument.Pages[findTextLocation.PageNumber - 1].AddElement(highlightRectangle);
        }

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

        // Write the memory buffer in a PDF file
        System.IO.File.WriteAllBytes(outputFileName, outPdfBuffer);
    }

    catch (Exception ex)
    {
        // The search failed
        MessageBox.Show(String.Format("An error occurred. {0}", ex.Message), "Error");
        return;
    }
    finally
    {
        // Close the PDF document
        if (pdfDocument != null)
            pdfDocument.Close();

        Cursor = Cursors.Arrow;
    }

    // Open the modified PDF document in default PDF viewer
    try
    {
        System.Diagnostics.Process.Start(outputFileName);
    }
    catch (Exception ex)
    {
        MessageBox.Show(String.Format("Cannot open highlighted PDF file '{0}'. {1}", outputFileName, ex.Message));
    }
}