Does the Google Drive scanner cache local copies on Android?
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:

/data/data/com.google.android.app.docs/files/fileinternal/


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.