How do I extract and move an embedded IDX file from an indexed PDF file?

Our client now requires our company to place PDF files, as well as an IDX file together into a sub-folder they can access. They are to have identical file names, just one file would remain a PDF, and it would have an identically named counterpart, but in IDX form.

I have learned how to embed an Index into a PDF file. However, I cannot figure out how to extract that indexed file and move it to the sub-folder.

Thank you.