It sounds like you're trying to just pick up what the printer has sent you and output it. What you actually have to do is somehow extract the die line from what he sent and set it up on a layer on an InDesign page that is the same size as the perimeter of the die line on its own layer. Lock that layer. create a new layer for the art and put that layer below the die line. Then copy and paste the art from the original InDesign file into position relative to the die line. I am assuming that the file the printer sent is full size, by the way. Once you have all of the art in position you will not need to have crop marks for it as the die lines themselves serve that function. If the printer wants a second pdf without the die line simply shut off the die line layer and export it as a pdf. If the die line is not done full size you may have to ask the printer—nicely— for a full size copy of the die line. If he sends it to you as a pdf, open it first in Illustrator and save it as an .ai file before placing it into the InDesign file.
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