It is usually a matter of the difference between “looks black” and “is black”. If I had a dollar for… nevermind, I digress.

You talked about opening in acrobat, removing pictures, converting grayscale, and adding in the pictures. You are right, not only should this be un-needed, but it is also unlikely to work well. It brings up a two points however:

First: If there is a color picture on the page that need to be removed, then the page is in color as far as the printer is concerned. There is nothing you can do about that.

Second: If you have acrobat PRO, open up your PDF and find “tools –> print production –> output preview” uncheck the “black” box. If the page is truly black, everything on the page should disappear. Do a similar thing in InDesign: turn on the separations preview (window –> output –> separations preview), and uncheck the black box. If EVERYTHING on the page does not disappear, then the page is in color. If it is black in InDesign, but color in Acrobat, then you are doing something wrong in your export. If it is color in InDesign, then you are doing something wrong in your design.

You need to do the first step above to start self-diagnosing where the problems are, then google or come back for more specific help when you have a more specific problem to report. In the meantime here are some common problems within the realm of “looks black” vs “is black”.

You are using the “registration” or “rich black” swatch instead of the “black” swatch for your text. Or you are using a swatch that looks black, but is really some form or “rich black”. Make sure that the swatch is 0:C 0:M 0:Y 100:K.

You are using a photo on the page that “looks black” but is really not. Only photos created as “grayscale” in professional software such as Adobe are “actually black”. If you are using a photo that you edited in some cheap or free software, such as Paint, then it is not going to be black, even though it may look black. (it has to do with RGB vs CMYK, these cheap things are mainly for making photos that “look” black and white to post to your facebook account or webpage.)

You are printing crop marks. Depending on how your printer handles this, it may just see a “color” element, and print in color.

Lastly, a 16 page book really has 4 pages on each sheet of paper. If any one of those 4 pages on the sheet has a mistake, and is in color, the printer has no choice but to print the entire sheet in color. Even as simple as one screwed up period in a sentence. That is why you need to look at the “seperations preivew” and make sure that everything disappears.

That's all I can think of. Good luck.