PrintDialog pDialog = new PrintDialog();

            if (pDialog.ShowDialog() == DialogResult.OK)
            {
                DirectoryInfo unzippedFolder = new DirectoryInfo(zibname);

              
                foreach (FileInfo file in unzippedFolder.GetFiles())//print each PDF-file within the unzipped folder
                {
                    ProcessStartInfo startInfo = new ProcessStartInfo();
                    startInfo.FileName = @"C:\Program Files (x86)\Adobe\Acrobat Reader DC\Reader\AcroRd32.exe";
                    Process process = new Process();
                    startInfo.Arguments = String.Format("/h /t \"{0}\" \"{1}\"", file.FullName, pDialog.PrinterSettings.PrinterName);//file.FullName: full path of PDF file                          startInfo.CreateNoWindow = true;
                    startInfo.ErrorDialog = false;
                    startInfo.UseShellExecute = false; 
                process = Process.Start(startInfo);
                    if (!process.WaitForExit(7000))
                    {
                        // kill Adobe Reader 
                        process.Kill();
                    }
                }

startInfo.Verb = “print”;