Protect Word Document When Download

[durga]

User downloads a document from a specified site, saves to the local disk and fills in confidential details. When other users logs on to this computer and if they try to access the file, the document should not be accessible.

Also consider that the document can be saved to a common server too, in which case, no one else other than the person who downloaded and filled the document should be able to open the document.

What are the options to achieve this??????????