Google Docs offers an intuitive platform to create and edit documents. You can add additional fonts by clicking on the. That's because Docs uses special web-based fonts (since it's a cloud-based app). It's not possible to add custom fonts to Google Docs at this time. You can only add fonts that are listed on that service. You can't directly add a new font however, as fonts for use on Google Docs are powered by their Google Web Fonts service. You have to set the language of the document first under File Language, and a font selection menu option will appear.
