Apple Insider posted a story that Apple won a patent for an early version of Preview app

The U.S. Patent and Trademark Office granted Apple's U.S. Patent No. 8,335,986 for "Previewing different types of documents," which describes the basic functionality of the current Preview app.

According to the patent's abstract, the property covers a "previewing application" for displaying a plurality of documents simultaneously in a single window, with the content appearing as digital books. Users can view pages in one or two dimensions and search through all opened document for specified keywords which are then displayed in an ordered fashion.

  Apple wins patent for OS X Preview app