Dear Maintainer,

The installation of this package should add the following line in /etc/apache2/apache2.conf and restart the Apache2 server:
Alias /manual /usr/share/doc/apache2-doc/manual

Indeed, the standard homepage (http://localhost) of the Apache2 server contains a link to manual ("Refer to this for the full documentation. Documentation for the web server itself can be found by accessing the manual if the apache2-doc package was installed on this server."), but this link points to nothing when someone clicks on it.
The alias above gives the solution to this bug.
Can you add that in a new release?
Thanks in advance.