You can customize the stylesheets used to render the documentation by adding style files to your project.

The html and htmlsingle render process uses the same set of customizations, so there are only two possible locations, one for PDF and one for HTML.

The files are located in your project under src/styles/pdf and src/styles/html respectively. The DocBook Framework only loads a file named custom.xsl file from the directory, which in turn can load additional files.