If you select an image and click the Edit Original button in the Links palette (or choose Edit > Edit Original), InDesign launches the program that created that graphic. Actually, it’s based on whatever application the operating system thinks should open the file.

So if you export a PDF from InDesign, re-import it into another InDesign page and then choose Edit Original, the PDF opens in Acrobat (not InDesign, of course).

The fastest way to choose this feature: Option/Alt-double-click on a graphic with the Selection or Direct Select tool.