private void button4_Click(object sender, EventArgs e)
        {


            // generate a file name as the current date/time in unix timestamp format
            string file = (string)(DateTime.UtcNow.Subtract(new DateTime(1970, 1, 1))).TotalSeconds.ToString();

            // the directory to store the output.
            string directory = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

            // initialize PrintDocument object
            PrintDocument doc = new PrintDocument();

            doc.PrintPage += new PrintPageEventHandler(this.pd_PrintPage);
            

            doc.PrinterSettings.PrinterName = "Microsoft Print to PDF";
            // tell the object this document will print to file
            doc.PrinterSettings.PrintToFile = true;
            doc.PrinterSettings.PrintFileName = Path.Combine(directory, file + ".pdf");


            doc.Print();

            //webBrowser1.Print();


        }


        private void pd_PrintPage(object o, PrintPageEventArgs e)
        {
            webBrowser1.Navigate("https://stackoverflow.com/questions/40812996/programmatically-provide-a-filepath-as-input-file-for-microsoft-print-to-pdf-p");
        }