My guess is whenever she requested a document from the classified system, someone at State printed it out then covered the classification and scanned it into a PDF and sent it to her on the unclassified email system.
This is why she keeps stressing her lack of knowledge of whether something is classified or not if the document isn't marked up as such and how she didn't know at the time that something was classified and that even the State Department doesn't have a clue. Mistakes were made. Whatever.
Every day, every hour as Secretary of State she HAD TO BE using and reading and discussing classified material - about our enemies, about our allies, and about our friends relations to our enemies/their enemies/and their allies, about our technologies and our defenses and defensive options and capabilities! ....
If she did NOT use and read and comment about classified information every day/hour/half-hour, she is either incompetent, unable, or “just-a-face”. Or all three.
Bingo! You got it. This will be the next fallback position. She didn't know it was classified information.