Could you please let me know the following details:
1. What is the version of Adobe Reader being used on your system? Is it 10.1.3? If not, please download and install the same from http://get.adobe.com/reader/
2. Are you using the 64 bit version of IE? If so, please switch to the 32 bit version of IE since the Adobe PDF plugin is not compatible with the 64 bit IE.
3. If you indeed have version 10.1.3 and are using the 32 bit version of IE , please let me know the exact bvehavior seen when you try and launch a PDF in the browser. Do you get an error or a blank page or something else.
4. Is the following checkbox checked under the Reader Preferences (Edit > Preferences > Internet)
"Display PDF in browser"