Open PDF file from your Java application

I have this help button in my application and I want that when the Help button is clicked, the User Manual in PDF format should be opened for the user.

 btnHelp.addActionListener(new ActionListener() {  
      @Override  
      public void actionPerformed(ActionEvent evt) {  
           if (Desktop.isDesktopSupported()) {  
                try {  
                     String userDir= System.getProperty("user.dir");  
                     String fileSeparator = System.getProperty("file.separator");      
                     String pdfPath = userDir + fileSeparator + "usermanual.pdf";    
                     File myFile = new File(pdfPath);  
                     Desktop.getDesktop().open(myFile);  
                } catch (IOException e) {  
                     JOptionPane.showMessage(null, "No PDF viewer installed.");                      
                }  
           }  
      }  
 });