IE9 doesn't reflect updated PDF file but instead reflects from cached version

Question

First, I apologise if this issue might be discussed/resolved somewhere, but if you have any solutions/ideas to what my issue might be, please help to share. And thank you in advance.
We have been using/filling PDF forms to generate dynamic FDF data. The URL/path to the PDF file is set inside the text/data of the generated FDF. The PDF file with the FDF data are shown to the browser. But with IE9, the browser always reflects cached version of PDF file, and not the updated version.  This is working fine for years in IE6..IE8, the updated PDF file with the dynamic FDF data are shown correctly. But in IE9, the FDF data is dynamically updated but the PDF file still shows the old version, which I think is from the cache.
In my testing, either I emptied the IE’s cache or set the Internet Option to check for newer versions of the page then it will reflects the updated PDF File. I tried Ctrl-F5 (to force refresh) too but no avail. I used Acrobat Reader 9 & 11, both having same problem, running on Windows 7.

Answer 1

Hi Pat. Thanks for your reply. 
Actually, I already been checking any IE9 options that might be different from IE8, and tried to change "Security" settings also but still can't get the updated PDF file. Maybe you have in mind where I can specifically check and try out?
I have tried IE10, but also encounter the same problem. sigghhhh
I have been using this for years but no problem, this PDF/FDF document application is developed/created using Acrobat Professional ver6 and FDFtoolkit.