Black colors don't match when export to PDF

The Preferences > Appearance of Black does influence the Options for Black on RGB and Grayscale Devices.

Printers, images and monitor screens.

It does not change the values in a PDF or Illustrator file.

A 100% black ink (which always reflects some light) is never as dark as an RGB black (which means the absence of light).

The preferences settings are just for display and export to image purposes.

If you want a darker black in your PDF, use the suggestions for rich black as mentioned in the other replies.

Depending on the printing workflow, I'll be inclined to use a manually input CMYK Rich Black color. Not every print setup will automatically convert 100% K colors in a PDF to Rich Black. However, for manually chosen Rich Black colors the total ink limit can vary depending on what type of print media is used (newsprint, vinyl for large format printing, photo print papers, etc). For instance 100% on all four CMYK ink colors is going to be a really bad idea on almost any kind of media. It's lots of fun discovering a color like that in client-provided artwork when using a thermal inkjet printer. The setting might be able to fly when using a latex-based printer, but it would still be overkill. 300 usually works as a general purpose total ink number for rich blacks.