PDF file
Alternative 1
A laser printer with double-sided printing should be used.
The PDF file from the main system is a double-sided A4 with a reserved area for two 190 mm labels. The remaining part of the first page may contain advertising, return instructions etc., and page two (on the back) may contain invoice/delivery note or similar.
Alternative 2
Recommended for e.g. printing labels on a thermal printer and single return labels on a laser printer.
The PDF file can be a single-sided A4 with a reserved area for a 190 mm label at the bottom.