hi guys
ive designed many things for commercial CMYK printing before but am having a slight problem with the requests from a specific printer

i'm exporting as pdf/x, and usually i choose the 'commercial printing' @ 300dpi option and never had a problem

however, this printer has stated that he requires 100% black for any black text in the file, and 20 20 20 100 black for any black backgrounds. how do i confirm/change this when exporting as a pdf?

ive looked around the forum but cant find a specific answer for this
regards
H