Running Policy Server and AdminUI, is a Policy Server restart needed after having changed the LDAP Pool Setting for User Directories?
No. There's no need to restart the Policy Server.
After having made the changes in the AdminUI, the Policy Server will open the new connections according to the configuration changes at the first access to its User Directory.
As per best practice, test the changes first in a lower environment before applying the changes in a Production environment to validate the operations.