Skim: Excellent free and simple PDF reader for Macs
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Have you ever felt that "Preview" in Mac isn't really powerful enough? If so, you'll appreciate Skim, which feels like a more advanced version of Preview and is ideal for viewing PDFs and scientific papers. Skim is specifically designed to help you read and annotate scientific papers in PDF, although it is suitable for viewing any PDF file. It is quite basic compared to Adobe Acrobat X and is a little unintuitive at times. For example, changing fonts should be made a little easier and there are far fewer capabilities when it comes to handling hyperlinks in PDFs. However, Skim does a tremendous job of making reading PDFs and note taking very straightforward. Most of the major features you need when viewing PDFs are included in Skim including adding and editing notes, highlighting important text, making snapshots for easy reference and navigation using table of contents or thumbnails, with visual history. Skim also features support for external apps such as LaTeX, SyncTeX, PDFSync, and BibDesk. It might not be quite Adobe Acrobat X, but Skim is an impressive free PDF reader and note taker that offers many of the features that Preview doesn't.