Unfortunately Axon doesn't support this feature, but IVM does (it lets you change the font size in the status window). This is a bit of an inconsistency that perhaps NCH should standardize across their VoIP software.
Note that you can always go to \ProgramData\NCH Swift Sound\Axon\Logs to read the log info (same as in the status window) and open the logs in notepad or your preferred text editor.