No registered application for this extension

When i try to open the downloaded document in opera,i obtained an message as " No registered application for this extension".Then i decided to open it through the foxit reader,but here i received an error message as " format error:not a pdf or corrupted"

The above error message tells that the document is not pdf or it may be corrupted.But actually I found file extension as pdf while i am downloading it.So the file may get corrupted.My suggestion is whether it may be beause of the document owner who does no wants to disribute or share the file.Below is the proof,