Skim

Free plan Mac

What Skim is

Skim is a free PDF reader and note-taking app for macOS, designed for scientific papers while also supporting other PDF files. Readers can search documents, add notes, highlight sections, bookmark files, and take snapshots for reference. Navigation tools include table-of-contents and thumbnail views, visual history, a reading bar, magnification, and smart cropping. Skim also offers full-screen reading and PDF presentations with built-in transitions. It works with LaTeX, SyncTeX, PDFSync, BibDesk, and other third-party applications, and AppleScript can access its windows, documents, pages, notes, and highlights. Skim stores notes and highlights in extended attributes rather than in the PDF itself. Emailing a PDF can therefore remove those annotations unless the transfer method preserves the 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 are listed for macOS 10.4 through 10.12. The project is described as free and open-source and developed by volunteer contributors. The listed Free plan costs nothing.

Who it suits

Skim suits macOS users who read and annotate scientific papers or other PDFs. It may be useful for people working with LaTeX or BibDesk, provided their file-sharing method preserves extended attributes when annotations need to travel with a PDF.

What it does well

Searches PDFs and supports notes and highlights
Offers full-screen reading and presentations
Works with LaTeX, SyncTeX, and BibDesk
Exports notes in several formats
Free and open-source

What to know first

Current release requires macOS 10.13 or higher
Emailing PDFs can strip notes and highlights
OCR support is not available

Limits

The free plan is the PDF reader and note-taker for macOS 10.13 or higher. Notes and highlights are stored outside the PDF data, and email can strip them unless the transfer method preserves extended attributes.

Plans

Plan	Billed and limits	Price
Free	macOS 10.13 or higher · PDF reader and note-taker	Free

As skim-app.sourceforge.io lists them, read 8 Oct 2026. The maker's own page has the final word.

Getting started

Open the Skim website.
Use a Mac running macOS 10.13 or higher for the current release.
Choose the free plan.
Open a PDF to search, annotate, or present it.

Verdict

Skim combines PDF reading, annotation, and presentation features for macOS. Keep its extended-attribute storage in mind when moving annotated files between devices or people.

Questions

How much does Skim cost?

Skim is free. Its Free plan is listed as free.

Which platforms does Skim support?

Skim supports macOS and is a desktop app. The current release requires macOS 10.13 or higher; older releases cover macOS 10.4 through 10.12.

Is Skim open-source?

Yes. The project is described as free and open-source and developed by volunteer contributors.

Can I export Skim annotations?

Notes can be exported as text or in Skim, PDF bundle, or FDF formats.

Does Skim support OCR?

No. OCR support is listed as none.

Facts from Skim's own pages

Annotation tools: Yes · skim-app.sourceforge.io, 24 Sept 2026
Automation: Skim supports AppleScript access to its windows, documents, pages, notes, and highlights. · sourceforge.net, 8 Oct 2026
Export: Skim can export notes as text and provides options to export notes in Skim, PDF bundle, or FDF formats. · skim-app.sourceforge.io, 8 Oct 2026
Free plan: Yes · skim-app.sourceforge.io, 24 Sept 2026
Integrations: Skim lists interaction with LaTeX, SyncTeX, and PDFSync, as well as integration with BibDesk and other third-party applications. · skim-app.sourceforge.io, 8 Oct 2026
License and project: The project wiki describes Skim as free and open-source and says it is developed by volunteer contributors. · sourceforge.net, 8 Oct 2026
Navigation: Features include table-of-contents and thumbnail navigation, visual history, a reading bar, magnification, and smart cropping. · skim-app.sourceforge.io, 8 Oct 2026
Notes storage: Skim stores its notes and highlights in extended attributes, so they are not stored in the PDF data itself. · sourceforge.net, 8 Oct 2026
Older versions: The project wiki lists older Skim releases for macOS versions from 10.4 through 10.12. · sourceforge.net, 8 Oct 2026
Password handling: Skim lists saving passwords in Keychain as a feature. · skim-app.sourceforge.io, 8 Oct 2026
PDF tools: Users can search PDFs, add notes, highlight sections, bookmark documents, and take snapshots for reference. · skim-app.sourceforge.io, 8 Oct 2026
Platform support: desktop · skim-app.sourceforge.io, 24 Sept 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. · sourceforge.net, 8 Oct 2026
Presentations: Skim supports full-screen reading and full-screen PDF presentations with built-in transitions. · skim-app.sourceforge.io, 8 Oct 2026
Supported system: The current release requires macOS 10.13 or higher. · skim-app.sourceforge.io, 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. · skim-app.sourceforge.io, 8 Oct 2026

Where Skim stands on Freedom251

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