Skim

Skim is a macOS application that lets users open PDF documents and add annotations such as highlights, notes, and snapshots. It includes navigation aids like a table of contents, thumbnail view, and a visual history, as well as a reading bar and magnification tools to focus on specific sections. The program supports full‑screen mode, built‑in presentation transitions, and preview of internal links for smoother reading sessions.

The software is geared toward anyone who works with PDFs, particularly researchers handling scientific papers, but it is also suitable for general PDF viewing. It integrates with LaTeX workflows through SyncTeX and PDFSync, works with BibDesk and other third‑party tools, and can store passwords in the macOS Keychain. Users can export notes as plain text and automate tasks via extensive AppleScript support.

Skim is open‑source and offered at no cost, running on macOS 10.13 or later. It provides customizable appearance options, Spotlight indexing, and remote‑control compatibility, making it a flexible choice for PDF annotation and reading on Apple computers.