PDF annotation tool for Mac OS What is the Mac OS application that provides most similar function as PDF annotator in Windows? 

I just want a program that enables simple annotating functions in Mac OS. 
Of course, freeware is preferred.

Add:
Thank you for recommending Preview. 
But I need a little more advanced features than Preview.
Any recommendation?
You can use Preview to annotate PDFs, make circles, arrows, texts, and even sign it.

It comes with OS X.