[SOLVED] Why isn't the 'Map colors' fixup removing background color behind text?

[scherz0]

I'm trying to remove the purple color that backgrounds quotations in this PDF. Unquestionably, it's too inefficient to delete every instance of the purple background singly and manually! I am using Windows 10.

1. I don't understand Dietrich von Seggern's abstruse answer. Please explain like I'm 5?

2. Please see the GIF below. Here's the PDF — call it BEK. I can't remove the background purple with CMYK = (16, 16, 4, 0).

3. This other PDF — call it McColgan — has this same glitch. I can't remove the background grey with CMYK = (0, 0, 0, 10).

 

[kerberos_20]

try GIMP image editor and change color to alpha,which is color without any color at all, its transparent, if you have white background it will be white, if you have black background, it will be black

GIMP

GIMP - The GNU Image Manipulation Program: The Free and Open Source Image Editor

www.gimp.org

here is small guide
https://smallbusiness.chron.com/replace-colors-transparent-gimp-52936.html