I opened it in Inkscape which is a vector/svg program.
I un-grouped the image and can move text and signature blocks around.
When I move them the white imprint is left on the green security paper.
I don’t use PDF files so not sure what to make of this.
Depending on the software used in the scan, it could have an image to text program that is used for filing. Basically, it scans the document and pulls out everything it recognizes as text and adds it as a separate layer to the scanned document can be content searched. Pretty common.