Catherine,
Exactly what platform are you using Microsoft Word on?
If Windows, if you create PDF by using Acrobat's Save as Adobe PDF (the PDFMaker feature) and you choose the High Quality Print joboptions, all your text in the PDF file will come out as Grayscale. This should meet the needs of your publisher (assuming that they know which end is up in terms of PDF publishing workflow). Grayscale is effectively the equivalent of CMYK=(0,0,0,K).
If MacOS, unfortunately, the PDF is always created as RGB where black is RGB=(0,0,0).
If you are creating the PDF on MacOS or your publisher can't understand that Grayscale is the same as Black, you can open the PDF file in Acrobat Pro and use the Convert Colors facility to convert the PDF file to CMYK, forcing RGB or Grayscale Black to CMYK=(0,0,0,K).
- Dov