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Dev tools · October 15, 2026

Theorem – Offline PDF/ePub reader that writes highlights to Local Vault

Read PDFs, EPUBs, and RSS feeds offline. Highlight, draw, and annotate — then sync to Obsidian or Logseq as plain Markdown. Open source. No cloud. No subscription.

Theorem – Offline PDF/ePub reader that writes highlights to Local Vault launched on October 15, 2026 with 6 votes, #715 of 3,508 launches that month and more than 75% of that year's launches.

Visit theorem.fundaments.work ↗Alternativestop 20% of October 2026

What it does

Theorem opens your PDFs, EPUBs and RSS feeds in under 50 ms, and writes every highlight straight into your Obsidian or Logseq vault as plain Markdown. No account, no subscription, no tracking. It works offline on Linux, macOS, Windows and Android. A native Rust parser gets 100 MB files onto the screen before you notice. Written to your drive with YAML front matter, ready for Obsidian or Logseq. An offline dictionary of 800,000+ words, with nothing sent to the web. Every highlight lands in your vault as a line of Markdown. There is no export step, ever. Pick a colour and click an underlined phrase. The file on the right is what Theorem writes to your disk while you read. Metaphysics, or the…from theorem.fundaments.work

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