Even high-end offset lithography leaves evidence that can identify the printer. If they know how it was printed, they can narrow it down. Just like police have all paint samples for cars to identify make/model in hit and runs, they have ink samples too. They can trace the ink, paper stock, printing press type. Printing presses are hard to hide.

All office and home printers from inkjet to laser printers insert a code that forensics can identify. Take a magnifying glass and look closely at the dots, you'll see it.