How can I change the background color that backgrounds only some text, in a PDF?

With vision difficulties, my grandpa can't read text whenever backgrounded by dark color in the PDF in the screenshot beneath. Click here to download it, or see some of its pages at Google Books. It's too unproductive to remove each use of the dark background color one-by-one. Thus how can I, in one brisk stroke?

I've Adobe Acrobat DC Pro, Foxit PhantomPDF, and Nitro Pro. Acrobat states no background to be removed. They and SensusAccess converted the PDF to a Word file's that's too deformed.

Answer

As I'm sure your grandfather will not read 2+2 with Pantone 302C printed edition, this should work fine for you. What we will do: convert everything to CMYK, then replace specific CMYK value with other and we will do that by using standard Acrobat Pro Fixups.

1. All the blues (100% and shades) in the document are Pantone 302 C color. You can check that by opening Tools → Print Production → Output Preview.



2. Open Tools → Print Production → Preflight and switch to Fixups.


3. Search for Convert All Spots to CMYK and run Fix. Now all colors in your document are CMYK.


4. Scroll to the page 22, as this is the first page with background fill you want to get rid of. Open again Tools → Output Preview and read CMYK value of the background. As I was converting Pantone with simulation to U.S. Web Coated (SWOP) v2, my CMYK values for background are 10:2:0:5. It's ok, if you will have different values. Just write them down as you will need to use them later.


5. Open Tools → Preflight and switch to Fixups. Then click Options → Create Fixup. Name your fixup whatever you like and fill in CMYK values for target and destination. In target and destination you must choose Destination/Alternate color model CMYK (%). Just click on the button and choose it from dropdown. Then click Ok and run a fixup.


6. Enjoy document without background. Here is your final PDF document with fixup applied.

P.S. Next time if you need to remove some other color, just change CMYK values for the same fixup and run it again. And be careful to check if there are any objects that shall not be removed but are in the same color; if so, this fixup will not be right choice.