PDF file does not get open from ShellExecute funct

Question

I am trying to open "Read Me.pdf" file after installation of my App finished.

I am trying to open this PDF file using

ShellExecute( NULL, _T("open"), csReadMe, NULL, csFileDir, SW_SHOWNORMAL );

and also tried

ShellExecute( NULL, NULL, csReadMe, NULL, csFileDir, SW_SHOWNORMAL );

May be, I have an issue regarding Adobe Reader 11.02 version, because in the earlier version of Adobe Reader that file was opening, while in AR 11.02 the Process is displaying in the Task Manager while ShellExecute() call, but Adobe Reader does not launch.

I am using VS 2012 with Win 8.

If I explicitly open that file or from the command prompt, then its easily open.

I dint find that what is going wrong.

Thanks in Advance.