It is not a matter of 'joining' the samba server with a linux client. It is a question of authenticating against the server. Pam is a set of modules that are used for authentication. When you have the correct module installed for pam - in this case it is libpam-ldapd - you then need to configure the settings in the files located in /etc/pam.d for authentication to occur. The usual way this works is when a user logs in to the linux client, the desktop manager (such as GDM) will check the name and password with pam, which checks with the samba/ldap server.
The home page of libpam-ldapd (formerly named nss-pam-ldapd)
http://arthurdejong.org/nss-pam-ldapd/setup explains how to configure the necessary files. The main ones are
/etc/nslcd.conf which specifies the details of the ldap server.
/etc/nsswitch.conf which specifies the name service switches.
files in /etc/pam.d - common-session, common-account, common-auth, common-password (Everywhere that pam_unix is called you should also call pam_ldap.)
Note - I had problems when trying to use samba shares as home directories. I eventually used NFS shares for this but if you have a mixed Windows and Linux environment you might need to design your own solution.