I'm working on a product packing design, so I need to have a barcode on the packaging. But when I attached the barcode PNG in Illustrator and exported the file to PDF format to print. The barcode turns out Gray color! I tried to "Unembed" the PNG and export it to PDF again; the barcode turns out normal. I don't understand why this is happening, and I'm not sure if it's ok that I do not embed the PNG and just send the file to the printer. So, questions: When I print the PDF file, will the "Unembed" PNG barcode still turns out normal?
You need to convert the PNG to the CMYK colour space before importing. When you export out to a CMYK PDF for print, the white can be discoloured during this process.