Skim

Open source; $0

Current Version: 1.3.6 (May 3, 2010)

Skim is an pleasing, powerful and essential substitute for Adobe Reader that also happens to be free. It is a both a PDF reader and note-taker, designed to help you read and annotate PDFs. Features include:

• Viewing PDFs
• Adding and editing notes
• Highlighting important text, including one-swipe highlight modes
• Making "snapshots" for easy reference
• Navigation using table of contents or thumbnails, with visual history
• View all your notes and highlights
• Convenient reading in full screen
• Giving powerful presentations, with build-in transitions
• Handy preview of internal links
• Focus using a reading bar
• Magnification tool
• Smart cropping tools
• Extensive AppleScript support
• Bookmarks
• Saving passwords in Keychain
• Export notes as text
• Automatic download of remote PDFs
• Support for Apple Remote Control
• Interaction with LaTeX and PDFSync
• Integration with BibDesk
• Spotlight support
• Highly customizable

Version 1.3.6 adds/changes the following:

• Optional Script menu, see the Wiki for details.
• Fix preference for automatic update checking.
• Fix preference control for PDF-TeX synchronization preset.
• Don't show PDF previews in presentation mode.
• Fix an exception on saving.
• Make secondary PDF views key on mouse down.
• Fix hiding Skim in full screen mode.
• Fix info window on Leopard.
• Search TeX editor in application bundle first.