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Actually only a high-end/professional printer would have the ability to open and interpret a PDF file without a computer. There are many printers that can open and print image files, but PDF file is much more complex and requires a "smarter" printer to begin with.
You would have better luck searching for a printer with Airprint, or direct wireless printing, where the printer can print a PDF file received from a smartphone. There are also some high-end printers that integrate with Google drive and browse and print files from that source:
https://www.google.com/cloudprint/learn/printers.html
It may also be possible to attach a tablet or phone directly to a printer using USB Host mode. Using a USB hub would give you enough USB plugs for both a printer and a flash drive. Using a special app it might be possible to browse PDF files contained on the flash drive and print them from the tablet directly to the printer:
http://printhand.com/usb_printers.php
https://play.google.com/store/apps/details?id=com.dynamixsoftware.printhand