Printing to PDF will allow you to include printer marks, including registration marks assigned with registration black (100%C:100%M:100%Y:100%K). However, you can add this registration color as a swatch that can be assigned to an object on the page, creating an on-page registration mark.

To add a registration color as a swatch: •From the Swatches panel, click Panel Preferences, then select Add Registration Color.

You can then apply the swatch to an object on the page.