You will need a separate NPrinting license key and control number. See: https://help.qlik.com/en-US/nprinting/November2017/Content/DeployingQVNprinting/Licensing-Qlik-NPrinting-Server.htm
If you are connecting to Qlik Sense Apps only, you do not need QlikView Desktop. If you plan to connect to QlikView documents, you will need QlikView Desktop installed on the NPrinting Engine machine. It must be licensed with either a local license or a Named CAL for the service account running the NPrinting Engine. You can use a leased license but it is not recommended as the lease could run out & revert QlikView Desktop to Personal Edition which is not supported.
HTH - Daniel.