Color PDF documents are generally great, but may not serve your purpose when you just want black-and-white printouts to save on printer ink. Fortunately, macOS High Sierra and the wonderfully versatile Preview app can convert colored PDFs to black-and-white document with a few clicks. But there’s a small bug you’ll have to deal with until Apple updates the Preview app and fixes the glitch. How to Convert Color PDFs to Black-and-White Thanks to a bug in Preview, there’s an extra step you’ll have to take when converting a color PDF to black-and-white or gray tone: first convert the PDF to JPEG in Preview, and then re-convert that back to PDF as you apply the Quartz filter: Open a PDF file in Preview. Go to the File Menu > Export. In the Export dialog box, you can choose to change the file name in the Export As field.