PDF Embed & HTML 5 Media won't appear on Item Pages

I’d like to have .pdfs and media appear on the Item Pages, and not just on the Files Pages. I see from a previous query that there should be a “Embed media on item pages” setting under the Settings admin section, but I don’t seem to have that setting. (We’re using a custom theme created by the Omeka Team.) Any idea what the problem might be?