You would like to utilize custom fonts with Office Web Apps Server 2013
We have seen several instances of customers using custom fonts with Office Web Apps Server 2013; here is our compiled list of information surrounding using custom fonts.
-Font files must be .otf files. We have tested extensively with .ttf files and they will not work with Office Web Apps Server 2013.
-The .otf files must be installed on the user's local machines, as well as every Office Web Apps server in the farm.
-Office Web Apps Server 2013 utilizes the Windows Font Cache for its fonts.
-The font files must be installed by an Administrator, and must be installed by right-clicking the font file and clicking Install. You may not simply drag the font file(s) into the fonts folder.
-Each Office Web Apps machine in the farm will need to be fully restarted before the fonts will take effect within the web apps.
-If you are viewing a document in the web apps that already has the custom font in use, the font will show in preview, view, and edit mode in the browser. Additionally, you will find the custom font in the font drop-down menu within the web app.
-If you are creating a new document in the web app, the custom font will not show in the default list of fonts. However, you may search for the font using the search feature within the font drop-down. Note that you must spell the font name exactly as it appears or the font will not be used. For example if the actual custom font name is "Fonts", and the user searches for "Font", the custom will not be utilized.
Jan 23 2017 edit:
Please note Office Web Apps Server 2013 and Office Online Server do not officially support the use of custom fonts at this time. However the above steps have been observed give you the best chance for custom fonts to work with Office Web Apps Server 2013 specifically.