Debian has a central utility to view all locally installed documentation, called doc-central. Other Debian packages for browsing Debian documentation include dwww and dhelp. The newer doc-central has several improvements over the previous tools, with an improved interface and requiring no further effort than installing the doc-base package.
Doc-Central is a collection of scripts that give you a convenient way to browse the documentation installed on your Debian system.
Doc-Central uses a local http server (like apache) to present a list of all registered documents. Depending on the type of document other tools are used to view the document: for info files we use info2www. All other types are currently linked to directly. To get the list of installed documentation the doc-base registration entries as used. For more information on doc-base please install the doc-base package and read the documentation in /usr/doc/doc-base.
it uses doc-base registrations for documentation. This means that unless maintainers register the documents for their pacakges doc-central won't know about them. So please check your packages to see if you register all the documentation.