I would do the following:

1. Test if your instance of IE+Google toolbar can open other PDFs from the Web.

2. Save a generated PDF and open it in a text editor. Does it start with %PDF- ? Are there any spaces or new line characters before the prefix?

3. Try to define the following HTTP headers in the JSP:
X-Download-Options: noopen
X-Content-Type-Options: nosniff

Here is some more headers to play with:

In order to switch the default HTTP headers of PD4ML taglib off, you would need to instal v360fx1b1 and define http=”noheader” attribute to