Google's business platform already had the ability to scan documents, but it can now match keywords or certain text strings to an admin-approved blacklist. It's designed to stop someone from sending something by mistake, but it can also potentially identify when an employee is purposely trying to share company secrets.
Currently, optical character recognition is only available to paid Google Apps Unlimited customers. That makes sense given you're unlikely to need protection from sending credit card details in an image file from your personal account. If you do feel your account could use some additional security, though, make sure that you enable two-step verification and keep training those spam filters.