This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
This isn't a JSP issue--it's a browser issue. You need to have your browser configured correctly to automatically open the PDF file in the same window as the webpage instead of giving you the dialog box. As far as your code is concerned, it's correct.