I print stuff, but I don't like wasting paper or ink. Research papers in PDF tend to be formatted for use in a journal. Chapters in PDF tend to be formated to use in a book. All have extra marginal whitespace. I found out today that OS X's Preview application can crop all selected pages at once. The steps are:
Choose the View menu's Thumbnails.
Select all the pages in the sidebar.
Choose the Tools menu's Rectangular Selection item.