fabrizioarnone

… Generating a list of only those tags assigned to the PDFs in a category will require a custom SQL database access to compile the list; thus the custom plugin. Also, the additional database access may have some performance issues depending on the size of your site. Are the possible performance impact and the requirement for a custom plugin acceptable?

Yes, the performance impact is acceptable. consider that the site is only dedicated to few dozens of person.

In other words, is the search form and research shortcode gallery on the “Protetto: prova” page you provided intended to be shown above the existing gallery on the “Governo e Parlamento” page you give as an example?

I would like to show the search form (in “prova” page) above the gallery (in “governo e parlamento” page). But when a user make a search I think that the user should see only the serp of the search and nothing else (not the gallery that he saw before the searc)

I hope you’ll understand and sorry for my bad english

here are two screenshot of what I would like to have…
https://drive.google.com/open?id=1bFO3wAVLa3dMhvvNia6sQN4AsPew53kc
https://drive.google.com/open?id=1HqsJyjrjfKdvz60XTO7oYF9MWNdWFODm

if this requires an extra payment please feel free to let me know!