In the past, you had to purchase Adobe Acrobat Pro to do some of the features OS X Preview does now for free! A couple of the features you may find useful:
- Annotate – Leave comments, markup using ovals and rectangles, and create links within the document or to Internet sites.
- Delete or Rearrange pages – You can now remove or change the order of your PDF pages within Preview.
- Merge PDFs – Take two or more PDFs and merge them into one document.
The article also lists other neat features of Preview that have to do with images. Check it out!