Select a printer in PrinterShare "Local Printers" list and click "Properties".
Here, you have an option to remove the printer from search results. This means that noone will see it in "Find Printer" dialog.
Open Automation dialog (Printer | Automation).
You can set a rule to handle documents from any sender (Anyone), or specifically for each user. You have following options:
If you are concerned that someone else might use your printers, you can set "Reject" as a default rule, and then allow printing to the required users only.