Why is my shipping label printing too small?
The print dialog is scaling the page. Fit-to-page and shrink-to-fit settings compress the label and its barcode; setting the scale to 100 percent or actual size restores full dimensions. On thermal printers the same symptom means the driver thinks it holds letter paper instead of 4 x 6 stock.
Why does my thermal printer produce a blank label?
Nine times out of ten the roll is in backwards. Direct thermal stock prints only on its coated face - scratch it with a fingernail and the coated side shows a dark mark. Flip the roll so that face meets the print head. A roll of thermal-transfer stock in a direct thermal machine gives the same blank result.
Is it OK to write over or touch up a bad barcode with a pen?
No. Barcode readers measure the width of bars and gaps, and hand-drawn corrections change those widths into gibberish. A flawed barcode calls for a fresh print of the same file, which costs nothing, rather than repair work.
Do I need a new label after a misprint, or the same one again?
The same one. A misprint wastes paper, not postage, so print the identical file again and discard the bad copy. Only when the information itself is wrong - address, weight, service - does the label need voiding and repurchasing instead.