rewrite rule generated with mpdf to a shorter version

I’m saving some pdfs into a folder with mpdf, the urls of pdfs are like this:

I want that if someone open this url it will show a shorter version like this:

how can I obtain this result using add_rewrite_rule() and apache web server?

UPDATE
as suggested I changed the code that generates pdfs in a way that are not stored in a local folder, but are generated everytime when visiting the url with a specified id parameter like this

so now the correct rewrite rule is