Trellis has a built-in setting to adjust the font size of your content and your headings.
Change the font size of your content
To adjust the font size of your content, setting you can go to Appearance → Mediavine Trellis → Display, then select an option from the Change Font Size dropdown under the Font Sizes & Typefaces heading.
We recommend a minimum of a 16px font to make sure your site is considered mobile-friendly, but Trellis will default to 18px. The line-height will adjust based on your font size selection.
The built in options for Trellis font sizes and line heights are:
Small = Font Size: 16px, Line Height: 26px
Medium = Font Size: 18px, Line Height: 29px
Large = Font Size: 20px, Line Height: 33px
X-Large = Font Size: 22px, Line Height: 36px
After you change the setting, click Save in the upper right corner of the Mediavine Trellis settings, then view a post to ensure that the adjusted font size is now displayed.
If the adjusted font size is not displayed, clear the Page CSS from Manage Trellis JS/CSS options in the admin bar, and clear any other caching plugins you might be using.