Skim
Skim is a free, open-source PDF reader and note-taking application for macOS, designed around scientific papers while also opening other PDF files.
What Skim is
Skim is a free, open-source PDF reader and note-taking application for macOS, designed around scientific papers while also opening other PDF files. It supports searching, notes, highlights, bookmarks, and snapshots, with table-of-contents and thumbnail navigation, visual history, a reading bar, magnification, and smart cropping. Full-screen reading and PDF presentations include built-in transitions. Skim lists integration with LaTeX, SyncTeX, PDFSync, BibDesk, and other applications, and AppleScript can access its windows, documents, pages, notes, and highlights. Passwords can be saved in Keychain. Notes and highlights are stored in extended attributes rather than inside PDF data, so emailing a file can remove them unless the transfer preserves those attributes. Notes can be exported as text or in Skim, PDF bundle, and FDF formats. The current release requires macOS 10.13 or higher; older releases cover macOS 10.4 through 10.12. Volunteer contributors develop the project. Skim has no OCR support listed.
Good
- Free and open-source
- Strong annotation and navigation tools
- Supports full-screen PDF presentations
- AppleScript access to documents and notes
- Exports notes in several formats
Watch out
- macOS only
- Current release requires macOS 10.13 or higher
- Notes can be lost when emailing PDFs
- No OCR support listed
Who it suits
Skim suits macOS readers who annotate scientific papers or other PDFs and need presentation, scripting, or LaTeX-related tools. It is intended for desktop use on supported macOS versions.
Verdict
Skim combines PDF reading, scholarly annotation, presentations, and automation features in a free macOS application. Its extended-attribute notes require care when sharing files, and OCR is not provided.
Plans and prices
From Skim's own pricing page, checked 8 Oct 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Free | Free | macOS 10.13 or higher · PDF reader and note-taker |
The facts
Each one read from Skim's own pages, with the date it was checked.
What it does
- Annotation tools
- Yeschecked 24 Sep 2026
- Automation
- Skim supports AppleScript access to its windows, documents, pages, notes, and highlights.checked 8 Oct 2026
- Export
- Skim can export notes as text and provides options to export notes in Skim, PDF bundle, or FDF formats.checked 8 Oct 2026
- Integrations
- Skim lists interaction with LaTeX, SyncTeX, and PDFSync, as well as integration with BibDesk and other third-party applications.checked 8 Oct 2026
- License and project
- The project wiki describes Skim as free and open-source and says it is developed by volunteer contributors.checked 8 Oct 2026
- Navigation
- Features include table-of-contents and thumbnail navigation, visual history, a reading bar, magnification, and smart cropping.checked 8 Oct 2026
- Notes storage
- Skim stores its notes and highlights in extended attributes, so they are not stored in the PDF data itself.checked 8 Oct 2026
- Older versions
- The project wiki lists older Skim releases for macOS versions from 10.4 through 10.12.checked 8 Oct 2026
- Password handling
- Skim lists saving passwords in Keychain as a feature.checked 8 Oct 2026
- PDF tools
- Users can search PDFs, add notes, highlight sections, bookmark documents, and take snapshots for reference.checked 8 Oct 2026
- Portability limit
- Emailing a PDF loses its extended attributes and therefore its Skim notes unless the file is sent using a method that preserves them.checked 8 Oct 2026
- Presentations
- Skim supports full-screen reading and full-screen PDF presentations with built-in transitions.checked 8 Oct 2026
- Supported system
- The current release requires macOS 10.13 or higher.checked 8 Oct 2026
- What it does
- Skim is a PDF reader and note-taker designed for reading and annotating scientific papers, and can also view other PDF files.checked 8 Oct 2026
Money
- Free plan
- Yeschecked 24 Sep 2026
Where it runs
- Platform support
- desktopchecked 24 Sep 2026
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