I've edited this quite a bit and bolded my question at this point. I realize that PDF won't be fully controllable in the browser, but that's not my issue here. My problem is, well, below in bold.
<div>
<object
data="${pageContext.request.contextPath}/UB04.xml"
type="application/vnd.adobe.xdp+xml"
width="415" height="500"/>
</div>
The XML is actually an XDP file; it gives dynamic data and a URL for a static PDF, and combines them in Adobe Reader. This displays in the browser as desired if it's a PDF, but when put in as an XDP, it takes control of the window and opens itself fullscreen to display the PDF. Serving an all-in-one XDP (with the PDF embedded as base64) has the same issue.
Help me make the XDP behave the same as a PDF?
Alternatively, if I can use iText to glue together the XDP XML and the static PDF template, I can serve the PDF directly, which seems to work just fine. Just not sure how to create PDF that route, which is somewhat underwhelmingly documented online.