Ubuntu – Convert pdf to monochrome black-and-white via command line

I have a 65-page PDF file that has text in a dark grey. (Actual text, not a picture/image of text.) Printing on my B/W printer, the text gets all blurry, because the printer is trying to make it less than black. I can solve this problem page-per-page by importing the pages to inkscape, selecting all paths, clicking on "Black", which converts all colours including the greytones to pure black, and exporting back to PDF.

Is there a way to do these steps in inkscape in the command line (for batch processing)?

Is there a way to achieve the same result (convert pdf to black and white, 1-bit greyscale) without inkscape?

_{Edit. There are similar questions on Unix.SE and on superuser, which use Ghostscript. However, these only convert the files to greyscale via the option -sColorConversionStrategy=Gray. The option -sColorConversionStrategy=/Mono results in the error Unrecoverable error: rangecheck in .putdeviceprops. Since my file is greyscale already, these don't solve my problem.}