What you can print on
Any working printer can produce a valid shipping label. The two common setups are: (1) a regular inkjet or laser printer on plain US Letter paper, with the label taped to the package, and (2) a thermal label printer (Rollo, Zebra, Dymo 4XL, MUNBYN) printing directly on self-adhesive 4×6 label stock. Carriers accept both — what matters is that the barcode is crisp, flat, and fully visible.
Print settings that matter
Always print at 100% scale — 'fit to page' or 'shrink to printable area' can distort the barcode enough to fail scanning. Use normal or better print quality; draft mode can produce faint bars. For thermal printers, select the 4×6 format when downloading your label so the PDF is pre-sized for label stock. Black-and-white printing is fine; labels never require color.
Attaching the label
Place the label on the largest flat surface of the package, not wrapped around an edge or corner — a bent barcode may not scan. Use clear packing tape over all four edges of a paper label, but never put tape directly over the barcode or address block, since glossy tape can cause scanner glare. Thermal labels are self-adhesive; press firmly from the center outward.
Common printing problems
Faint or streaky bars: replace ink/toner or clean thermal print head. Label prints tiny in a corner: page scaling was set below 100%. Barcode smudged: the label got wet before the ink dried — reprint rather than risk a failed scan. Printer offline: labels are standard PDFs, so you can also save the file to a USB drive and print at a library, office store, or print shop.
No printer at all?
Most carriers offer label-free drop-off options for some services (like USPS Label Broker or UPS/FedEx store printing), but these usually require carrier accounts. The simpler route: your label PDF can be printed anywhere — a friend's printer, a print shop, or an office store. The label doesn't expire the moment it's created, but ship promptly since postage rates are date-sensitive for some services.