No application is associated with the specified file for this operation

string UrlName = Url.ToString();
            string DownloadFilePath = @filePath+"\\"+FileName;
            if (File.Exists(DownloadFilePath))
            {
                File.Delete(DownloadFilePath);
            }
            //Downloading file from Http Url
            WebClient myWebClient = new WebClient();
            myWebClient.DownloadFile(UrlName, DownloadFilePath);            
            System.Threading.Thread.Sleep(1000);
            //Code for Print the PDF file
            Process P = new Process();           
            P.StartInfo.FileName = DownloadFilePath; // FileName(.pdf) to print.
            P.StartInfo.WindowStyle = ProcessWindowStyle.Hidden; //Hide the window.                        
            P.StartInfo.Verb = "Print";
            PrintDialog pd = new PrintDialog();
            //PrinterSettings setting = new PrinterSettings();           
           
            P.StartInfo.Arguments = pd.PrinterSettings.PrinterName.ToString();
            pd.PrinterSettings.MaximumPage = 1;
            P.StartInfo.CreateNoWindow = true; //!! Don't create a Window.    
            P.Start();
            P.WaitForExit(4000);
            P.CloseMainWindow();