Pgpool-II documents are written in SGML (more precisely, DocBook, which is a language implemented using SGML). To generate readable HTML documents, you need to compile them using docbook tools. To install Docbook tools on RHEL or similar systems, use:
yum install docbook-dtds docbook-style-dsssl docbook-style-xsl libxslt openjade
Once the tool sets are installed on the system, you can compile the docs:
$ cd doc $ make $ cd .. $ cd doc.ja $ make
You will see English HTML docs under doc/src/sgml/html, and online docs under sgml/man[1-8]. Japanese docs can be found under doc.ja/src/sgml/html, and online docs under sgml/man[1-8].