As Alex said N-Printing 16 is single thread 32 bit. So you have to kick off the job's sequentially. Not sure if you can use task dependency like we do in QMC. After Task1 finishes run Task2, something like that.
Where as other option would be to upgrade to 17, which i believe it is multi thread and can run parallel.
I am on 16.2. As far as I know the NPrinting engine does not support multiple threads. It is sequential. If you have multiple tasks, then it will be finished in sequences (first come first serve).
I tested it and it took sometimes to finish 5 tasks. The five tasks are identical, and at the end I asked to send me an email. I only got 3.