This is not a one-step solution, but it would give you what you want:
Choose File > Package. At the bottom of the dialog, click Report... This will save a text file with all the information you'd want about the file, including the path of all linked graphics. If you wish to could create a PDF of that text file, and merge it or send it along with the PDF for the document.
I'll give it a shot -- thanks! The iamge-path information doesn't necessarily have to be in a PDF, so a text file with the same filename as the PDF layout might just do the trick.