The easiest way is to try it (that is what I would do). However, if they can print it they can always get it back into a regular PDF and measure there. May not be as accurate, but is a way around what you are trying to prevent. They could also do screen captures and such. You need to consider all the possible ways they could get the information and work from there as to what might be workable. My guess is that if you really want to restrict it, someone will find a workaround and you will lose. For the average user it may not be a problem and will work as desired.
The media file for any rich media annotation can easily be extracted from a PDF, unless you apply a method of security (such as DRM) which prevents the file from being opened in third-party applications. This is why you are shown a warning message when embedding a b-rep PRC file. The obvious solution is to alter the model prior to conversion to PDF so the measurements are wrong - e.g. by tesselatting and over-simplifying the meshes.