Apple - Is it possible to crop multiple pages in Mavericks Preview.app?

Yes.

1. Open a PDF.
2. If not already enabled, View → Thumbnails.
3. Select some pages (click first then select all; command+click or shift+click)
4. Use the rectangle tool to select region on page. (On versions of OS X prior to 10.9, you should see a preview of the selection on other pages too).
5. Select Tools → Crop (or Command+K). All your selected pages should be cropped.
6. Save or Save As.

This is only possible when editing a pdf. It isn't possible to apply a single crop to many images that are in separate files. In order to do this, one way would be to

1. Combine the images into a single pdf
   • Open all of them in a single window.
   • Use "Print" then "Save as pdf."
2. Use the technique described in the other answer to crop all pages of the resultant pdf.
3. Split the images back out into separate files using a variety of techniques, such as Automator's "Render PDF Pages as Images" function, or on the command line using ImageMagick as described here.

Note: if you're willing to use the command line, you might just want to use ImageMagick directly to crop all of the images.