I learned the tricks of Preview from an article online, sometimes it is hard to access it, so I copy it down in this article
1- Annotation- You can add arrows, circles, text and lines over pictures, PDFs and anything else you open. You can even annotate a link onto a file.
2- Change Files Kinds- Convert files from one kind to another, quickly. You can convert pretty much any file into a PDF. You can even open up a bunch of app specific files like Photoshop, Illustrator or Pages. And then change them into a PDF or web ready picture.
3- Easy Edit Tools- Change the file size? Change the pixel size? Crop? Change the color? Yep! The most useful of the simple edits from iPhoto can be found under the 'Tools' menu. They are easy to use and understand.
4- Soft Proof Preview- Ok you may not be as graphic geeky as me, but what this means is you can see how your picture will print; the cool thing is you can use all of the Apple color profiles to do it in. Geek out.
5- Build a PDF From Anything- Yes, you can convert from a single file, but you can also build a multi-page PDF from any assortment of PDFs. You can even add blank filler pages. I like to smash together assorted PDFs and turn them into one document just for fun. Did I mention you do this by dragging and dropping? When you save your PDF, you should check out the 'Quartz' filter drop down menu in the 'Save As' window. It gives you a few iPhoto like edits to apply to the entire PDF doc.
6- Import From Whatever You Want- Sure you can open files, but you can also import them directly from your camera or scanner. (of course this may depend on the usefulness of the drivers for said peripherals) Also, you can tell Preview to take a screenshot (from a selection, window or the entire screen) and do what you want with it. You can import from your clipboard. You can even open animated GIFs and look at each frame in the thumbnails.
7- Send Directly From Preview- Take your newly annotated multipage PDF and e-mail it to your work colleagues. Or take those imported images/files and send them to iPhoto or Aperture.
8- Use Preview for a Slideshow- It has a command just for this. This is great for sharing a PDF on screen. You can also do Pages, Numbers and Keynote documents. And try this: open a bunch of photos at once (use shift or control to choose multiples) and then view those as a slide show. Since it opens them in one window and gives you the thumbnails in the sidebar, you can change the order too. I like this for slideshows more than iPhoto, because it means I don't accidentally share my embarrassing cat photos.
9- Add Keywords to Your Files- Personally, I think keywords are the essential search tool of the future. If you have 20 documents that are similar but not the same, adding keywords will save you 10 minutes opening 20 files, 30 times to find the exact one you're looking for.
10- Take Yourself Out of That Old Background- Use the Alpha selector to remove areas of color. Use the Lasso to remove busy areas. This means you can take your ex out of your Facebook profile pic. And you should. You can change the window background color in the general Preferences; this may help you see your photo for editing better. This can also be useful to take a profile pic into a chat program.
11- Bonus! The first bonus is that you can view any attached GPS info of a photo, via the 'More Info' tab in the Inspector. The second is that Preview can view .DAE files (Digital Asset Exchange files). DAEs are documents that include 360 degree views or 3D information. These files are often animated and can rotate around you, the viewer. This is a new feature and newer technology