Service workers are installed per domain. When the user visits a page with the JS script, a service worker is installed for the user for that particular subdirectory. Then, all pages in that subdirectory that the user visits subsequently would be automatically optimized. However, if you would like to optimize only a few pages with Dexecure, contact us at email@example.com and we can come up with a script that helps you optimize only certain pages of the website.
Nonetheless, we suggest adding the optimizing code to all HTML files that are directly accessible to the user, allowing the Service Worker to install regardless of the which page a new user lands on your website.