How do I make text 100% black rather than CMYK black at PDF export?

[Gamerprinter]

I am encountering a problem with the printer for the documents I've prepared with the Printer's Mark PDF export.

Here's a quote by the printer with the particulars:

With regards to the text, I think it might be that you've got your text set to use the 'registration' colour (C:100 M:100 Y:100 K:100) rather than the 'black' colour (C:0 M:0 Y:0 K:100). Registration over-saturates the paper with ink, losing precision especially in text. The problem should be fixed if you can change all paragraph styles to use 'black'.

I didn't see any function in the File/Printer Settings dialogue box to force black to stay 100%.

Is there a way I can ensure I get this right?

Edit: I found some old threads discussing this problem - I will read up on it and see if I can fix it referring to them. Thx.

Michael