SaveFileDialog opf2 = new SaveFileDialog();
opf2.Filter = "HTML (Результат) (*.html)|*.html";
opf2.ShowDialog();

using (var converter = new Converter())
{
converter.ConvertToPdf(Convert.ToString(opf2.FileName), Convert.ToString(opf2.FileName + ".pdf"));
}
// Show the PDF
System.Diagnostics.Process.Start(opf2.FileName + ".pdf");
}