--css command-line option
By default, pasdoc generates a pasdoc.css file in the generated documentation in HTML and HtmlHelp formats.
If you want to use your own style sheet, you can use the CommandLine option --css=CSS-FILE-NAME. Then pasdoc will simply copy the given file CSS-FILE-NAME to the output directory as pasdoc.css.
You can find some alternative stylesheets on PasDocCssExamples.