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PDF Tools vs Skim: catalog facts
PDF Tools	Skim
Free Free and open source under the GPL-3.0.	Free Free and open source under the BSD licence.
Windows, macOS, Linux	macOS
Reads and annotates PDFs inside Emacs Search and link navigation	SyncTeX integration makes it the standard viewer for LaTeX work Annotation and snapshot tools designed for reading academic papers
Only useful to Emacs users Requires building or installing the epdfinfo server	macOS only Notes are stored in Skim's own format unless explicitly embedded
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0	License: BSD-3-Clause
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 24, 2026	Official website Full listing and sources Checked September 22, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.