.riv files should not be downloadable from Preview Links

Technically obfuscation and data encoding to base64 blob is possible, however on internet you can access and extract any data, so that's not really feasible... If you're doing previews for your client before they pay for your work, you'll have to use either watermark or adding some kind of failsafe in your created file (like a timed watermark that appears after x seconds).

Got it, thanks!