Images will always be embedded.
You need to select appropriate options for image quality, compression and color handling.
That only thing that *can* happen: if you save the file with "preserve Illustrator editing options" and then that company open the PDF in Illustrator, then the images are probably not embedded in the Illustrator part of the file. They are still in the PDF though. If they are actually doing that, then it would be better to send them a packaged AI file. I mean, you never know how much the person at the other end knows about workflows ...
... View more