How can I no-index specific PDF files in my Avada Wordpress media library so that they don't appear in search results?

I'm trying to no-index specific PDF files in our Avada Wordpress media library so that they don't appear in search results. We have yoast SEO plugins but I contacted their customer service and yoast explained this isn't possible via their plugins. Does anyone know how to do this? I've scoured search engines for an answer and I'm not finding one, there doesn't seem to be anything in the settings that I can see to do this.