Convert all text's color in PDF to black while ensuring text is selectable

Question

Looking for ways to change the color of all text in a PDF to black using an open-source command-line tool (or package) while ensuring that text is rendered as text.

Thanks to some answers on SO, found a command to convert the PDF to grayscale.

gs -o op.pdf -sDEVICE=pdfwrite -sColorConversionStrategy=Gray -f ../ColorTest.pdf

Input PDF:

Output PDF:

PDF Sample here

However, the requirement is for the text to be black.

Any detailed steps or pointers on how this can be accomplished would be highly appreciated.

Answer 1

cpdf -blacktext ColorTest.pdf -o out.pdf