I’m just trying to get a better understanding of what the plugin can and can’t do. When I am using the live load archive option, like on https://env-fmsbsite-redev.kinsta.cloud/publications/, am I limited to only show results contained in that archive? In other words, it cannot display PDFs, is that correct? Can only the plugins own results can do that?
Yes – basically a post type archives are limited by WordPress, usually the final query is overwritten even if a different post type is forced, non-archive post types are then removed automatically.
The plugin’s own results can do that, those can display anything anywhere basically. If you want to display different post types on the archive I would recommend doing that instead.