If you find that PDF files aren't updating after changes, it could be that they are cached by the browser or a CDN such as Cloudflare.
If you are running on Apache then you can modify the mod_headers block in the /public/.htaccess file to prevent PDF file caching:
<IfModule mod_headers.c>
# Blocks Search Engine Indexing
Header set X-Robots-Tag "noindex, nofollow"
# Prevents PDF File Caching
<FilesMatch ".pdf$">
Header set Cache-Control no-store
</FilesMatch>
</IfModule>