Increase the Contrast of a PDF to Sharpen & Darken Text

With Preview you can adjust the contrast of a PDF, this makes the text sharper and darker, and for scans or dubious quality PDF’s this makes them significantly easier to read.

• Open the PDF with Preview
• From the ‘File’ menu, choose “Export”
• Click on the “Quartz Filter” drop-down menu and choose “Lightness Decrease”
• Choose “Save”

For a very practical example, I noticed this was sorely needed after downloading Guy Kawasaki’s freely available “The Macintosh Way” book, which is a great look at early Apple history. Unfortunately the PDF’s text is very light making it difficult to read, but the Quartz Filter mentioned above greatly helps this. The downside you may notice with some files (including The Macintosh Way) is an increase in noise. That noise is most noticeable on older PDF’s of scanned books or documents, and at times the trade-off may not be worth it.