Section 30.5 Font Size
The overall (document-wide) font size may be given as one of eight different values, ranging from 8 points to 20 points. The default is 10 points. These values influence multiple settings within LaTeX itself, and PreTeXt will also adjust some default values, such as the line-width (in order to preserve an optimal number of characters per line for reading ease). See Subsection 44.3.4 for precise details.