Reason: the Density value is high
1. Set the print Density value to about 4 in Preview( Mac system)
Please note: If you use the PDF software of Preview, the fond and barcode are deepened automatically.
2. open the PDF file via Adobe Reader to print, the density value is 8-12
3. For windows, go to label printer--manage--printing preference-page setup-density--(8-12)