I looked around and couldn't find the cached images or PDFs. But that doesn't prove they don't exist.
Our specific need is for our scan to go straight into Drive, with no stops along the way that can be tracked later. We have a regulatory imperative to save to a secure site and not leave anything on our phones (or tablets).
Interestingly, fidelity isn't that important, just that the scan has been saved in Drive and not locally.
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.
Q & A