Hi,
I have use below code instead of Desktop class code.

                                 response.setContentType( "application/pdf" );
				response.setHeader("Content-Disposition", "attachment; filename=PACTHelp.pdf");
				String fileURL = "D:\\PACTHelp.pdf";
				URL url = new URL ( fileURL );
				URLConnection conn = url.openConnection();*/
                                //Use the username and password you use to
			       /* String authentication = "Basic " + new                sun.misc.BASE64Encoder().encode("kirti.adsul:december".getBytes());
				 System.getProperties().put("proxySet", "true");
				 System.getProperties().put("proxyHost", "ttilproxy"); // your proxy host
				 System.getProperties().put("proxyPort", "80"); // your proxy port
				 conn.setRequestProperty("Proxy-Authorization", authentication);*/

				 BufferedInputStream  bis = new
				 BufferedInputStream(conn.getInputStream());
				 BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream());
				 byte[] buff = new byte[2048];
				 int bytesRead; 
				 // Simple read/write loop.
				 while(-1 != (bytesRead = bis.read(buff, 0, buff.length))) 
				   {
							bos.write(buff, 0, bytesRead);
					}

but it unable to open pdf file either file because it
either not supported file type or file has damaged. is here any missing ?

first "Hi" is printed. But before "Hi1" code gives error that given as above.

Means IReportRunnable design = engine.openReportDesign(rptdesign); line having that error.