Is it possible to set up a search function that returns a list of actual PDF files as apposed to a list of posts that the PDF is attached to?
I am not sure if it's near to your requirement or not.
However it might be little helpful to you.
[[LINK href="https://wordpress.org/plugins/media-category-library/"]] https://wordpress.org/plugins/media-category-library/[[/LINK]]
After installing above plugin do the necessary settings by visiting <strong>Settings > Media Category Library</strong>
Then create new categories by visiting <strong>Media > Media Categories</strong>. Like <em>Reports</em>
Then assign all your pdf to that category.
Finally you can create some page for serch and add this shortcode <strong>[mediacatform]</strong>. It will allow user to search for medias(in our case pdf) in different categories with keyword.
If this plugin is near to your need you can hire a developer to modify it :)
Did you get any solution?