you can export PDFs with various restrictions for quite some time on MacOS (X)… at least 10.7 but probably even before. Which version of MacOS (X) are you running?
Apple has some info for the latest MacOS versions here - but I think since Tiger you can use pdfauxinfo or an Automator workflow (there is an Automator action to protect a pdf with a password) to achieve this (info here), here is a description with pics on how to do it in Preview, or here. The interface might differ slightly but at least the print to/export as PDF will have some option to set a password.