private void convertToPdfButton_Click(object sender, EventArgs e)
{
    // Create a PDF document
    Document pdfDocument = 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
    PdfPage pdfPage = pdfDocument.AddPage();
            
    // Set user and owner passwords
    if (userPasswordTextBox.Text.Length > 0)
        pdfDocument.Security.UserPassword = userPasswordTextBox.Text;

    if (ownerPasswordTextBox.Text.Length > 0)
        pdfDocument.Security.OwnerPassword = ownerPasswordTextBox.Text;

    if (pdfDocument.Security.UserPassword != null && pdfDocument.Security.UserPassword.Length > 0 &&
        (pdfDocument.Security.OwnerPassword == null || pdfDocument.Security.OwnerPassword.Length == 0 ||
        pdfDocument.Security.UserPassword == pdfDocument.Security.OwnerPassword))
    {
        // A user password is set but the owner password is not set or is identical to user password
        // Set a different owner password
        pdfDocument.Security.OwnerPassword = pdfDocument.Security.UserPassword + "_owner";
    }

    // Set PDF document permissions
    pdfDocument.Security.CanPrint = printEnabledCheckBox.Checked;
    pdfDocument.Security.CanCopyContent = copyContentEnabledCheckBox.Checked;
    pdfDocument.Security.CanEditContent = editContentEnabledCheckBox.Checked;
    pdfDocument.Security.CanEditAnnotations = editAnnotationsEnabledCheckBox.Checked;
    pdfDocument.Security.CanFillFormFields = fillFormFieldsEnabledCheckBox.Checked;

    Cursor = Cursors.WaitCursor;

    string outPdfFile = @"DemoAppFiles\Output\PDF_Creator\Set_Permissions_Password.pdf";
    try
    {
        // Create a HTML to PDF element to add to document
        HtmlToPdfElement htmlToPdfElement = new HtmlToPdfElement(urlTextBox.Text);

        // Optionally set a delay before conversion to allow asynchonous scripts to finish
        htmlToPdfElement.ConversionDelay = 2;

        // Add the HTML to PDF element to document
        pdfPage.AddElement(htmlToPdfElement);

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

        // Write the memory buffer in a PDF file
        System.IO.File.WriteAllBytes(outPdfFile, outPdfBuffer);
    }
    catch (Exception ex)
    {
        // The PDF creation failed
        MessageBox.Show(String.Format("Create PDF Document Error. {0}", ex.Message));
        return;
    }
    finally
    {
        // Close the PDF document
        pdfDocument.Close();

        Cursor = Cursors.Arrow;
    }

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