It would be worthwhile to ask why? This is very uncommon. If you are dealing with a printer that cannot print separations from a PDF file then you need to find another printer.
Yeah, i used to have PDF writer or whatever but IT locked me out - I ended up making the sep PDF through InDesign.
It wasn't for a printer - LOL
This is very uncommon.
No it's not. It's very commonly done to provide pre-separated pages to local silkscreen shops. Eliminates mistakes; simplifies workflow for people who often don't really understand color separation. Enables them to print their screen positives on non-PostScript printers.
Years back, in FreeHand, it was even easy to ensure that separation-specific custom halftone settings survived the trip.