If barcodes are not scanning using PDF

Check the barcode on the item matches the barcode on the scanner - then also check item settings on what barcode is listed

If all matches use the word pad from the scanner to see what barcode is scanning physically on the items barcode

example below shows the barcode printed as 076818014072 but the physical barcode printed doesn't have the check digit printed 

Usual fix will be to have the alternate barcodes listed in The Order Exchange without the check digit