The hosts.lpd file provides:

A.
A list of network printer IP addresses.

B.
A listening of printers available on the local network.

C.
A listening of computers that have printer (lpd) daemons running.

D.
A listening of hosts allowed to use printers on the local machine.

E.
A list of hosts on the local network that are not allowed access to printers attached to the local
machine.

Explanation:
The /etc/hosts.lpd file defines which remote systems are permitted to print on the local system.
Only that hosts specified in /etc/hosts.lpd can send the printing job.
See the output of /etc/hosts.lpd
Station1.example.com
Station2.example.com
Station3.example.com
Only station1, 2 and 3 can send the print job.