CMYK black line art shows as gray in Pages

I'm creating a document that I need to print in CMYK. I changed each PNG image from RGB to a CMYK PSD. When I put the images into Pages, they are showing as gray. I can tweak them with the sliders, but it seems odd I should have to do this, and it's over 100 images, so it will take a long time, plus I don't trust it to stay black. I need the line art to stay black.

When I insert the same image in RGB or in Grayscale, it shows as black with no need to use the sliders.

Initially I was using Acrobat to convert the whole document to grayscale and CMYK but I had some inconsistent results so decided to change each image to CMYK and start all over. Now I've hit another roadblock. How can I get black line art? Should I go back to using Acrobat and how can I achieve black lines there (each page also has some gray dashes that originated in Pages and I want those to stay gray)? I don't know InDesign and don't have time to learn. Thanks for any help.