How to increase contrast for faint text in a PDF?

To increase the contrast in the PDF, there are adjustments available in Preview that may do the trick.

Open the PDF in Preview.

• Then do Tools > Adjust Color
• First try Auto Levels
• If that's not enough to bring out the text, manually adjust the three sliders below the Histogram to work on bringing out the faint text (they control the Black level, Midtone level & Highlights level). You may have to play with these.
• You can also manually adjust the Contrast, Highlights & Shadows sliders. They are both an alternative to and an adjunct to the Histogram sliders.

You can always Reset All if you do not like the results.

If you are looking for a cheap and rough solution then maybe this? -->

Copy the text and paste it to a Text Edit or other text editor that doesn't support higher level font features.

MartinR wrote:

Then do • Tools > Adjust Color

I think your method will only work if the text is just an image of text, not actual text. I opened up a PDF where the text is rendered as text and I highlighted a line. The Adjust Color feature is not active. In my file I used Tools > Text selection When I copied it and pasted it to a TextEdit document it displayed as the default font and size I use for TextEdit documents. My TextEdit Settings are set to use plain text.

Search for “Edit PDF contrast” in the App Store.

You may be right about that.

As a test I opened a few different PDFs and the Adjust Color feature was available for some but not others. And it wasn't just text documents saved as a PDF, it was also in a document I had scanned to PDF.