Hello Peterschneider,
Sorry for the delayed response and inconvenience caused. As per the description above, you want to print a color PDF into true black, Is that correct?
On Windows, you can print all of the non-white colors in your PDF file as black, resulting in a simple monochrome printout. Printing as black is useful for printing PDFs that contain text only, or for printing engineering drawings that have lightly colored lines.
- Click File>Print.
- Select Print Color as Black, this prints colors as solid black, not in shades of gray.

Note: If the checkbox is dimmed, click the Advanced button. Make sure that Acrobat Default is selected in the Settings menu of the Advanced Print Setup dialog box.
3. Click Ok to Print.
You can also make custom settings/changes in Advanced Printer Setup, for detailed information, please refer to the following Adobe articles Color conversion and ink management (Adobe Acrobat Pro)
Advanced PDF print settings, Adobe Acrobat
You can navigate to File>Print>Click on Advanced>Under Color Management>You can select Black and White in Color Profile

By making the changes, you can print the color PDF in black.
You can also refer and try the suggestions from the following Adobe articles Cannot print to PDF in black and white
https://acrobatusers.com/forum/printing-prepress/bw-print-colour-pdf/
Let us know how it goes and share your findings.
Regards,
Anand Sri.