The properties of the font can be changed from the 'Font Properties' panel which is located under the 'General Options' tab. The general font properties defined in he 'Font Properties' panel will be applied to every text element of the chart unless a style has been defined to override the default settings. This means that if a font style has been defined for a certain text element then it will not be affected by the default font properties.

Font Properties panel
Following parameters are used for defining properties of the font which appears on the canvas:

Generic font properties applied to the text that appear on the canvas
If the 'Show advanced options' check box is selected - some additional parameters will be displayed in the 'Font Properties' panel. These additional parameters are used for configuring the properties of the font which is displayed outside the canvas this includes text elements such as; axis names, data labels, legend etc.
Following are the advanced parameters that cam be used to change the appearance of the text which is displayed outside the chart canvas:

Generic font properties applied to the text displayed outside the canvas