Use FileMerge to diff PDF files Dec 01, '09 07:30:03AM • Contributed by: peter ljunglöf As a university teacher, I often get to read new versions of student essays, and I want to be able to quickly see what changes there are from the old version. Here's how to use the FileMerge application (included in the Xcode developer tools) to view PDF files. In addition, you'll also need the command line uti