The PDFs display CBS with mathematical typography rendered using LaTeX and the CBS-LaTeX macro package.
Names are highlighted, and name references are hyperlinked to declarations.
Pretty web pages corresponding closely to the PDFs are generated from the same sources using the CBS-KaTeX macro package and rendered using KaTeX.
On macOS (Catalina), the Preview app does not support hyperlinks to specific targets in PDF pages; similarly when browsing PDFs in Safari. Acrobat (Reader) and Firefox support hyperlinks in PDFs just as in web pages.