The pdfBytes on a ReportVersion is the actual PDF document that was generated when the ReportPackage was rendered. Piper stores it in the database so you can download any historical version at any time without regenerating it. This is important for regulatory compliance: you need to be able to produce the exact document you submitted to an agency years after the fact, even if the underlying monitoring data has since been updated. Because pdfBytes is stored permanently, the submitted version is always retrievable.
Technical section
Data model, API, and internals — visible to developers.