The Display PDF in browser option controls whether you can view PDFs by opening them in a browser using the PDF plugin. It does not control what happens when you double click a file in Windows Explorer. I'm fairly certain that you will never automatically open the PDF in a browser unless you open it form the browser (e.g. File > Open).
Install the latest updates. There was a bug where a specific reg key was disabling the Manage Interent Settings. If that doesn't work, repost.
Thanks for the quick reply.
We have now taken all the updates available, the preferences had been set
to not check for updates.
Now the linked PDFs open in Internet Explorer without the Security Block
In this situation we were not opening from Windows Explorer, we have an
xml file which opens in Internet Explorer, the xml file has links to PDFs
on the network and the PDFs have links
to other PDFs. The user needed the linked PDFs to open in Internet
Explorer for ease of navigation, testing that there are no broken links.
Thanks so much for your timely help we really appreciate it, the issue is