It does not matter if your source chart has text wrapped or not because to create a Pivot Table in Excel you must uncheck the Keep Source Formats check-box.
You cannot simply make changes in Excel PivotTable formatting as they do not persist. This has nothing to do with NPrinting but is an Excel limitation. You can test with any Excel Pivot Table without involving NPrinting in any way. The way to format PivotTables is to use one of the in-built PivotTable styles. Or create your own. Here is a video.
HTH - Daniel.