Google has just finished rolling out its new online marketplace for third-party applications designed to enhance Google Drive. Google says that the marketplace is available from within Google Docs and Sheets, and can easily be accessed by clicking on the add-on tab at the top of a documents page. There have been chrome extensions that integrate into Docs before, but this is the first time that Google has released an official marketplace for apps that directly integrate.
Called Add-On's the apps are created by third-party developers and enhance the service by adding handy features such as the ability to sign documents, create custom templates, add images with annotations, and quickly generate macros for spreadsheets. Other apps allow users to quickly and easily cite sources, write footnotes, and build bibliographies by simply searching the web for the desired sources.