Export to pdf

InDesign

go to file> export

choose format> Adobe PDF (Print)

choose preset PDF/X1a:2001
choose the relevant or all pages
export as pages, not spreads, for single pages and booklets

if needed, you can add crop marks and export!

Illustrator

go to file> save as

choose format> Photoshop PDF

File:Export Phot1.png

you can select specific pages or all of them

choose preset PDF/X1a:2001

if needed, you can add crop marks and save!

Photoshop

go to file> save as

choose format> Photoshop PDF

File:Export Phot 1.png

choose preset PDF/X1a:2001