Install a copy of xpdf on each machine and a web server on one of them and and you can pull lots of PDFs and serve them out to your network of RPi's.
You can get a lot of PDFs on a 32GB SDCard. With a Fuji USB SDCard reader you can add another 32GB card and fill that . With some careful planning you could get videos (as MP4s) and serve them out from one of your RPi's.
This century you shouldn't need to print on lots of dead pulped trees.
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