SHORT VERSION: The Google Drive Scanner will, by default, leave cached versions of the PDF file it creates. I still hope to find some setting that will turn off this caching.
LONG VERSION: Here's how I figured it out.
I have a rooted droid (Note2) I used to do some testing. It has BusyBox and a couple of good terminals installed. After getting into the root shell ('su'), and from the root position in the filesystem ('/') I ran the following command
find -iname *jpg -mmin -2
immediately after taking a pic with my camera. It found the new pic just fine. I then ran the same command after using the Google Drive Scanner. Nothing showed up. That's good.
I ran nearly the same command but changing the name:
find -iname *pdf -mmin -2
immediately after using the Google Drive Scanner. The find command located PDF files cached in this location:
Now I have to determine a way to manage those caches (this is all about HIPAA data for my company).
Hope this is helpful to someone.