I'm trying to print a document, but the Epson L3210 shows an error message related to paper.

This typically means the printer detects a paper jam or that the paper size/type settings don't match the loaded paper. Open all access covers and carefully remove any jammed paper, ensuring no small pieces are left behind. Check the paper guides to make sure they are snug against the paper stack. Verify the paper size and type selected in the print settings match the paper loaded in the tray.