I use Ubuntu 11.10, and I want install phpdocumentor. I use the tutorial How to install PhpDocumentor on Ubuntu. But:
If you navigate to
http://localhost/PhpDocumentor/(note that the URL is case sensitive) you will find the installation ready to run.
I get a 404 Page. Maybe something should be set up in virtual - hosts?
Perhaps check the file permissions on the files and directories under /var/www. Like how www-data "needs to own" the output directory where files get written by apache, it's possible the file permissions on the webpage files need to be owned also... they might not accessible due to being installed by root via sudo. So, if /var/www and the phpdocumentor files under it are not owned by www-data, try changing the ownership (sudo chown -R www-data /var/www/PhpDocumentor) and see if that solves it.
Of course, if you don't see the /var/www/PhpDocumentor directory at all, then that's the problem... the "sudo pear config-set data_dir /var/www" command earlier in the tutorial should have made sure that the installation puts the files there.