I would like to convert an Illustrator document to a PDF and make it available to graphic designers doing publicity. It would be convenient if the designers could turn off the different layers but I don't want to leave the art items editable.
Not really. If a PDF has layers, it is editable.
Generally Illustrator PDFs can always be edited to a degree unless the content was rasterized before saving as PDF. The ease of editing is effected by the "retain Illustrator editing" option, but that doesn't really remove any standard editing, merely complicated appearance editing.