What does it show?

The PDF contains black letters and graphics that are incorrect from a printing point of view.

How to interpret the result?
The PDF contains a black letter or graphic that is not 100% black, but made of a mixture of 4 colors.

PDF 100% black font or graphics error.

What does the warning mean?
Checking 4-color black font
When printing, these letters or graphics may not have nice contours. The readability of the text deteriorates.
Not 100% black text.
The following converter corrects the error if all four colors are between 50-100%.
If the letter or graphic is included as an image in the PDF, the error cannot be corrected.
How the problem could be resolved?
Converting 4-color cmyk font to 100 % black.
cmyk black font, 100% black font