Also Ganesh I don't know if it is helpful to you but I found multiple copies of every pdf I have opened or modified in folders that look like:
\AppData\Local\Packages\microsoft.windowscommunicationsapps_8wekyb3d8bbwe\LocalState\LiveComm\
(This is apparently the metro cache folder and seems to store copies of all pdfs)
The Att folder specifically seems to have hundred of folders with an 8 digit Hex value. An error I got when I tried to force a change of the properties of a pdf was, "The requested operation cannot be performed on a file with a user-mapped section" I'm
pretty sure these copies of the pdfs in the LocalState->LiveComm directory are whats causing all the problems since they are seemingly what makes Windows think that the pdfs are open somewhere else.