I used to hate it when I would click on a jpeg file and Preview would jump in and open it. No, I wanted Photoshop! But when I found out that Preview could do the same simple edits (rotate, crop, resize and save as) in less time than it took good ol’ Photoshop to load my life was changed.
Now here is another reason to love Preview, combining pdf document. Read this article from ProfHacker to discover how simple it is.
Sorry Windows users, Preview is only available on a Mac.