Question: Can I change the font type or size associated with a DesignPLUS theme?
Answer: With only a few exceptions (some headings and some of the navigations) the templates do not do anything to change the default Canvas font. To override a font, your CSS needs to be as specific or more specific than the element(s) you are trying to change. You can inspect an element using your favorite browser and track down where the font is set and then write something similar to your global CSS file to override.
Regarding font size, we recommend being very careful about making font size decisions that impact all content. Such a decision can have unintended side effects on the Canvas UI and cause issues for your students. If you study up on recommendations for web font size, you will find that the 16px, which is the default for Canvas and web browsers, is the recommendation. Browsers are designed to allow users who want a larger font to easily increase the font size.
In the future, we hope to make themes flexible so that you will be able to pick and choose aspects from pre-built themes to customize your own themes easily.