How do I de-index pages?
There's more than one reason why you would want Google to de-index (delete from their records) a page on your site:
The page no longer exists
Serving a 404 page is perfectly normal and should be the way to go in this case. Just remember to fix any link that might still pointing to the non-existent page. You can do this by running a search for the link in your WordPress dashboard, going to any page that has the link, removing it, and updating the page.
Google will eventually remove that page from their index, but if you want to accelerate the process, you can go to your Search Console and request a URL removal.
The page exists, but you don't want it in Google
It's possible to hide pages from Google's search engines, so the page stays up but Google doesn't see it. However, this can be quite a technical process that can result in your whole site being deindexed if done wrong. If you're in this situation, get in touch with us (firstname.lastname@example.org) and we will help you though the process.