What is this application that you are using to open PDFs in a browser?
PeopleSoft HRMS, so the client is a typical web client.
Does it work correctly on "normal" web pages, e.g. the PDF links near the bottom of http://forums.adobe.com/community/adobe_reader_forums ?
In a 32-bit browser, the PDFs should open inside the browser.
With a 64-bit browser, the PDFs will open in an external Adobe Reader window.
For the PDF links you provided at the bottom of the page, it works the same. It always opens in the external Adobe Reader.