Set the content-type of the response to "application/pdf",
ex. response.setContentType("application/pdf");
Add a dummy parameter on the end of the url, like: http://x.y.z/DoGenCompStmt?filename=dummy.pdf
because IE ignores content-types, so you need to give it a hint, and the ".pdf" extension is an easy way.
Set the "content-length" on the response, otherwise the Acrobat Reader
plugin may not work properly, ex. response.setContentLength(bos.size());
An additional thing that seems to help some IE browsers is to also have :
response.setHeader("Content-Disposition", "inline;filename=somepdf.pdf");