Cut two pages by Preview at once
Yes, this can be achieved solely with Preview.


Show page thumbnails by clicking Thumbnails from the View Menu.


Show the Edit toolbar, and choose the Rectangular Selection tool.


Select the rectangle that you want to crop each page to.
Select (⌘-click) all the pages that you want to crop in the page thumbnails.

The pages don't have to be sequential, and you can select all pages with ⌘A.
Click Crop in the toolbar.