It is likely that you do not have a dedicated NPrinting Service account and that you do not have a dedicated named CAL manually assigned to the dedicated NPrinting server service account. This is typically the root of the access violation error.
If you continue to have issues after checking the above, please log a case via the Qlik Support site in order to effectively assist you with the issue.
Though it is not an NPrinting Server (but an NPrinting Designer) issue the cause is the same yet the fix is slightly different. A CAL should be assigned to the o/s user that runs the NPrinting Designer executable.