public ActionResult DownLoad_File()

        {

            return File(ScLiu(PathUrl), "application/octet-stream", "sb.pdf");

        } 

public Stream ScLiu(string path)

        {

            using (System.IO.MemoryStream memStream = new System.IO.MemoryStream())

            {

                WebClient webClient = new WebClient();

                var obj = webClient.OpenRead(path);

                return obj;

            }

        }