Not. It’s not necessary to refresh your meta data if you want to send your reports. You only need to refresh your meta data if you created new objects (or changed it) and you want to use those objects. You only need to reload your Qlik app.
Refreshing metadata will also reset the QV.exe sessions which NPrinting keeps and therefore will insure that new data is loaded into reports.
The June 2017 release (due out in a few weeks) includes the ability to schedule metadata reloads so that you can do this before running Publish Tasks to distribute reports to ensure new data is loaded into reports.