How do I “Limit access to uploaded files”

I do not see in the Settings section where to enable “Limited access to uploaded files”
My situation is that non-logged in users to my site can access files located under
“https://…/wp-content/uploads/xyz.pdf”

Some background information. My site is on WordPress.com Business Plan – where I can install plugins but not modify any files such as “.htaccess”. WordPress.com uses nginx.

I contacted WordPress support and they state that “its not possible to restrict access to the wp-content/uploads/ directory at WordPress.com”

Thank you.