Font size Ubuntu 18.04 LTS

Current MATE on Ubuntu 18.04 LTS. How does one adjust the font sizes set by the window manager defaults in an application? Most of the applications (including the licensed-for-fee PDF Studio Pro current) have GUI command fonts (and the buttons upon which these commands appears, such as "file") that are too small. Using MATE tweak, and others, I have changed default fonts, but this only changes some of the widget tags (e.g., "file"). Is there a command/GUI application that shows which font an application is using by default, and also to change these (particularly the point size)?