Change font size, font family in all confluence page

[Bhakti Honmute]

I want to change font size, font family to my confluence site, how can I do it? 

[Bill Bailey]

If you are on the cloud version, you can't. That is a server/data center feature. You would either have to install a theme from the marketplace or create your own (but the notes make it sound like you can't at this point in time due to a change in UI).