When you install the NPrinting server you will get one default folder where all your NPrinting files can be placed and you can schedule the same. NPrinting server will automatically pick all the .nsq file in this folder and as per the schedule in the .nsq it will get executed . so once you have schedule and if you want to change you need to edit the .nsq file , instead of that If you want to make this schedule from external configuration (Through XML code) you can give the XML target folder .
2.On-Demand : Is nothing but a extension object in qlikview kind, using which you can run the NPrinting task from Qlikview files : go through this link
you need to create that ...go to files and create new and file which will get generated will be in .nsq format...for Qlikview if you create a file it will get saved in .qvw format in the same way in NPrinting the file will get saved in .nsq file format