They are likely referring to Typekit fonts. These fonts are not packaged. Additionally, even packaged fonts require that you have a properly paid for license.
May I suggest that as a service to your clients that you subscribe to CC so you can properly work with them?
Thanks, Bob. We recently got approved to upgrade to CC, we just haven't had any down time to install yet. Should be a temporary problem, but we do need to turn these documents around pretty quickly. For now, we're just going to update the graphic elements and send it back to them for text edits.
Thanks again, Mr. Levine. I've been using this forum for over fifteen years and I think you've personally answered a couple hundred of my questions. I probably owe you tuition!
Just install the CC Desktop app and sign in. Open the file and you should be prompted to sync the fonts that are missing.