There are several ways to change font name or font size in HippoEDIT.

Font face or font size settings in HippoEDIT is syntax related and so should be changed in syntax related settings. For example to change font for Plain Text documents (files with extension *.txt or *.log) you need to go to Tools->Options→Syntax Settings→Plain Text→Fonts & Colors and then change font name in Font combo. The first entry in the list (normally called Use from Default) tells HippoEDIT that font name should be taken from parent syntax schema. List of parent syntaxes is shown in breadcrumb control on top. For example Use from Default mean, inherit font name from default schema.

If you want to change font name for ALL syntaxes, just change font name of Default syntax schema. All other schemes inherited from it and by default use font name of it.

To jump to the Font & Colors setting for current language faster you can use (when some document open) or context menu on Overview bar or Tools→Syntax settings (here is name of current language) shortcut.

The easiest way to change the font size is using the mouse wheel, keeping Ctrl. Another way is with the help of status bar, where you can as select some predefined scale factor or enter an exact value. Font size changed in such way is not persisted, and reset in the new session to the default value.

To change in fixed manner, you can use the way described for Font face.