Can't open pdf/word/excel/ppt using android file manager?

Hi guys, I installed the Android app "ES file explorer" on my Playbook with OS2 and it allows me to browse company's file server shares on the domain network. But when I try to open any of the files like word, pdf, excel, ppt etc, it gives me an error message and won't open. pictures files can be open no problem. Have any of you been able to do what I'm trying to do?

If I use the free Air Browser to browse files on the PB, it can open files no problem.

Thanks.