It would be great to have a way to hide media assets from search indexes.
We do store some ‘subscriber only’ type content in the CMS and would prefer to keep that private. Don’t need passwords or anything, just don’t want the item showing up in searches.
+1, we recently noticed the same need.
Hello ! + 1 ! Also the same need to hide from indexes search media assets as PDF. Thank you in advance to make a step towards that direction 
Just a note that while we currently don’t support setting a noindex directly on media assets*, crawlers shouldn’t be able to find them on their own unless you’re linking to them from somewhere… if you set nofollow on those links everywhere on your frontend, they shouldn’t show up in indexes.
Another workaround is to use a serverless proxy to hide the real URL, and you can apply any sort of protection you want to that proxy (referrer checks, robots.txt on the whole domain, etc.).
* But proper “secret” URLs is something I’d love to see too! Please keep voting on this and hopefully we can properly support this in the future.