Do you already know that you need to create your own Product Style as explained here?
https://www.adoc-studio.app/blog/css-stylesheets-asciidoc
When wanting to define the PDF style, you'll have to find first the area starting by
Footer or header of the pages are already defined in the base style called Base.adocstyle included in the app bundle under Contents > Resources > FactoryStyles > …
To modify the footer and header on your PDF style, you can copy the related blocks from the style.css of the Base.adocstyle and paste in the style.css of your product style.
To insert a static text before the automatically rendered chapter name or page number, just enter the Text in "" before of after the chapter name or page number placeholders.
Here a sample of how my style places header and footer on left and right positions.
The violet header is defined by the Base.adocstyle upon which my style is based.
I hope this helps you further 🙂