File serving was not very easy, because there is a relationship to the headers that I cannot solve now, and this is one of those issues where the effort put in trying to find a fix is more easily solved by working around it: instead of, as what I am trying now, display .pdf files in the browser, I might as well serve everything as direct download.

Well, in fact the map of nginx easily solves this. I had a hard-coded add_header Content-Type for .pdf files, but this is much better. Just ensure the map directive goes under http and not server, or the routes.

http {

	[...]

		map $request_uri $mime_type {
			default "application/octet-stream";
			~\.(pdf)$ "application/pdf";
			~\.(mkv)$ "video/x-matroska";
			~\.(ipynb)$ "application/x-ipynb+json";
		}

	[...]

		server { 

			[...]

				/route/ {

					[...]

						add_header Content-Type $mime_type;
				}
		}
}