Ok, for the dokuwiki default template the font is set in file
css/basic.less. Just look at the top section:
body {
font: normal 87.5%/1.4 Arial, sans-serif;
/* default font size: 100% => 16px; 93.75% => 15px; 87.5% => 14px; 81.25% => 13px; 75% => 12px */
-webkit-text-size-adjust: 100%;
}
As an example put the following code in your
userstyle.css[/m] to overwrite it with the font [m]Courier:
body {
font: normal 87.5%/1.4 Courier, sans-serif;
}