How to watermark multiple PDFs on a mac

Hi,

I have around 100 PDFs that each need to have the same watermark. I've read that a batch sequence may be the answer but i can't find the 'advanced' menu option- does it have a diferent label as i'm using an apple mac?

is acrobat even the right program? i have access to indesign and photoshop if either would be better.

Any help would be greatly appreciated,

Thank you