Skim is a PDF reader and note-taker for OS X. It is designed to help you read and annotate scientific papers in PDF, but is also great for viewing any PDF file. Skim requires OS X 10.10 or higher. Features Viewing PDFsAdding and editing notesHighlighting important text, including one-swipe highlight modesMaking "snapshots" for easy referenceNavigation using table of contents or thumbnails, with vi