I am trying to make a design for a book's double page. The design is composed by vector art (made with Illustrator) and a photo.
The artwork PSD file is set as A3, 300 DPI, 8 bits CMYK.
One of the pages have a introduction small text, which colour I set to CMYK (0, 0, 0, 100). The text was typed using Photoshop's text tool. Once finished, I save as high quality printing PDF, with JPEG compression of 600 DPI for images above 600 DPI.
I sent the PDF for a professional printing service, but it looks like the black 100 was converted to black 400 CMYK (100, 100, 100, 100) because it is blurry and have what looks like a magenta shade...
What am I missing? Would it be the PDF export process?
I tried to be as many specific as possible... I'm sorry if I wasn't, but I don't even know how to ask Google about this problem.