OGNL expressions look on the value stack. Scriptlet variables are not on the value stack. The *easiest* thing to do would be to put the scriptlet variable into a JEE scope (page or request, probably): OGNL expressions *can* access scoped variables.
Really, though, this is a Bad Idea, and there's almost *never* an absolute need to do this.
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