Google Docs add-ons work similarly to how a browser extension works. They are a third-party app that you install to Google Docs to gain additional features. Some add-ons increase productivity (like proofreading tools) and some add more extensive capabilities (like allowing teachers to integrate grades into students papers). Here’s how to install them and some of our favorites.
To get an add-on, open a new or existing file in Google Docs, click “Add-ons,” and then click “Get add-ons.”
You can browse the list of all add-ons, use the drop-down menu to sort by category or search using the search bar. Once you find an add-on you like, click the “Free” button to install the add-on (if it’s a paid add-on, this button will reflect the purchase price).
Read more: https://www.howtogeek.com/401363/the-best-google-docs-add-ons/