Blog post is located here https://www.pdftron.com/blog/webviewer/automate-facial-redaction-of-pdfs-with-javascript
To run this example, you only need to have files server from any web server. If you have npm installed on you computer you can use http-server serve the content locally.
npm install -g http-server
http-server .
or if you don't prefer global npm package installs you can use npx
npx http-server .
You can access it via browser on you localhost http://127.0.0.1:8080