Even before the dawn of the digital copiers there some were a few copiers that allowed you to mix different size originals in the copier document feeder. For instance if you had a mix of letter, legal and ledger size documents you could place them all in the feeder an as long as you had the corresponding paper in the paper trays. The copier would then pull the right size paper from the correct paper draw. However, this feature with the older analog copiers slowed the copiers copy process down to a crawl!
Today, there is not that much of a need for copying mixed sized originals, but every now and then we do get someone that needs to enable that feature. The good news is that all digital copiers should have this as a standard feature.
I sell the Ricoh brand of copiers and the mixed size original feature is located in the "special features" ( I think that's it ) on the home screen of the system. It's not a feature that a user will see from the home screen. Users will need to select that feature and then place the documents in the feeder and the press the start button. I'm still amazed at how many customers are still "wowed" by this simple feature. Copying mixed sized originals is not as slow as the analog systems anymore however you do need to allow some additional time since the paper is drawn from different paper trays. Usually if a customer needs this feature we will put it into a program key for easy retrieval.
BTW, for those of you that scan a lot, you can scan mixed sized originals with most of the Ricoh systems.