Many have asked how to show people their files, but not allow them to download copies for themselves. This sounds like a reasonable request.
Unfortunately, you cannot prevent this. You can prevent access to files behind a login, but once you reveal the file contents, it can be copied.
We can make it more difficult for the user, such as preventing hot-linking, streaming our video or disabling right-clicking, but we cannot ultimately prevent the file’s contents from being copied once it is viewed.
This image shows the first files being loaded into Firefox for WordPress.com