Your question has many potential meanings:
1. Can you still use your PageMaker that was the basis of the upgrade? Yes.
2. Can you create doents in InDesign and save them in PageMaker format? No.
3. How do you send files for output to printshops and pre-press shops that don't have InDesign? Send them PDF files. If they can't deal with PDF files, then find a different shop.
Even back in my PageMaker days (now four years ago), I'd stopped sending native PM files to printshops. I used PDFs then and I still do now. I have never considered sending native InDesign files for output.