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.
Probably you should have asked in the Portlets forum.
However, Portlets are multiple applications running on a single page being presented by the portlet container. Most commonly if a portlet is going to invoke some other app, it would be a full-blown webapp and not a portlet, and the invocation would be via a hyperlink.
What you're contemplating would be a directive to the portlet container to display an alternative container webpage. However, when you do that, every portlet is "active" at the same time. It's the user's choice as to which pane within the page to send input.
An IDE is no substitute for an Intelligent Developer.
I’ve looked at a lot of different solutions, and in my humble opinion Aspose is the way to go. Here’s the link: http://aspose.com