By making the size of the body type in the entire site larger, that increased the size of the font in the left widget in the footer — the one that has a link to our own websites and appears on all normal pages and posts.
Since there is no option provided to amend that I went into the HTML for the text of that widget and added the following code:
<span style="font-size: 80%;">
Text in the left footer widget
Amazingly, WordPress let me do that! I think that makes the pages look neater.