Not sure if this is the right place but.
I have a Matlab app that creates PDF files of various data.
I want to include a GEOJSON string in the more info section of the metadata
I attach an example of how this looks in another application.
I searched around and ended up here -
Thanks
Try adding it to the Description tag.
exiftool "-Description=JSONSTRING" file.pdf
Otherwise, run the command in FAQ #3 (https://exiftool.org/faq.html#Q3) on a file that already has the correct data to see the location.