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

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