Configuring pureftpd

Grab a copy of pure-ftpd from http://www.pureftpd.org. At the time of this writting the current version was 1.0.11
There is a README.LDAP. Read it.
configure with
./configure --with-ldap
make all install
You may want to install a pre-compiled binary package for your system. Make sure it was compiled with ldap support.
Setup a LDAP configuration file in addition to the standard pure-ftpd.conf file.

    LDAPServer ldap.ispman.org
    LDAPPort   389
    LDAPBaseDN o=ispman
    

and you are ready to go.
run the server with the option
/usr/local/bin/pure-ftpd -l ldap:/etc/pureftpd-ldap.conf