PDF Embed API and fit width / height

I am trying to set "Fit width" and "Fit height" without using the Page Control overlay, i.e. have my own buttons and then use a API calls.

I cannot see what the buttons in the panel trigger, and I cannot find anything about this in the documentation -- so I am wondering if this is possible at all.

I've tried using apis.getZoomAPIs().setZoomLevel(some_calculated_zoom), but I've yet to achieve the same result as the Page Control buttons do

Anyone know if there is some API call I can use, or if there is some kind of workaround?