@hitesh789 - Is this happening with any other files, or is it just Doc files? Also, how large are the files? The more information you can provide, the better the chance others will be able to suggest a solution.
@hitesh789 - Hmm. Very strange. Have you taken the common WordPress troubleshooting steps of disabling all plugins and changing your theme to see if that helps? If you can't do that on a live site, maybe you can clone the current site and use that as a test environment.