Document properties of the PDF (IG Report) show it was created by a scan software, and last modified by an Adobe plugin that does OCR.
Most likely because of the redaction and to not have them be a layer in the published report's PDF that can be removed by editing software. But that's just my guess.
Here's the doc's properties – you can look them up for yourself and look up what
PFU ScanSnap Manager is and what
Adobe's Paper Capture Plug-in does.