First let's check the rpcclient man page. Here are two relevant passages:

adddriver <arch> <config> Execute an AddPrinterDriver() RPC to install the printer driver information on the server. The driver files should already exist in the directory returned by getdriverdir . Possible values for arch are the same as those for the getdriverdir command. The config parameter is defined as follows:

Long Printer Name:\
Driver File Name:\
Data File Name:\
Config File Name:\
Help File Name:\
Language Monitor Name:\
Default Data Type:\
Comma Separated list of Files

Any empty fields should be entered as the string “NULL”.

Samba does not need to support the concept of print monitors, since these only apply to local printers whose drivers can use a bidirectional link for communication. This field should be “NULL”. On a remote NT print server, the print monitor for a driver must already be installed before adding the driver or else the RPC will fail.

setdriver <printername> <drivername> Execute a SetPrinter() command to update the printer driver associated with an installed printer. The printer driver must already be correctly installed on the print server.

See also the enumprinters and enumdrivers commands to obtain a list of installed printers and drivers.