Developer Runs Free Local AI in SumatraPDF
A developer connected a locally run AI model to the open-source SumatraPDF reader as an alternative to Adobe's paid AI features.
Updated on Nov. 14, 2026 in Artificial Intelligence
Live Poll
Would you pay a monthly subscription for AI features in your PDF reader?
A developer connected a local AI model, Qwen3.6-35B-A3B, to the free, open-source PDF reader SumatraPDF, letting users chat with a whole PDF or explain, summarize, or translate highlighted text. The setup offers AI features that Adobe charges $24.99 a month for in Acrobat Studio.
Why it matters
The setup shows that AI-assisted document reading can run entirely on a personal computer without a subscription. It offers an option for readers who want AI help with PDFs without paying Adobe's recurring fee.
The test ran Qwen3.6-35B-A3B on a personal PC with a 64K context window, generating 69 tokens per second and answering the first question in 12.5 seconds and later ones in 4 seconds. SumatraPDF stable 3.6.1 passes only about the first 1,000 characters of highlighted text, while the 3.7 pre-release passed the full 1,531-character selection.
The players
Adobe
Adobe is a software company whose Acrobat PDF products include paid AI features sold through subscription tiers.
SumatraPDF
SumatraPDF is a free, open-source Windows PDF reader known for its lightweight design and support for external helper tools.
The details
The helper uses the free PyMuPDF library to extract text page by page and passes it to a local llama-server instance through SumatraPDF's External Viewers and Selection Handlers settings. Alt+1 opens a chat about the whole PDF, Alt+2 through Alt+4 explain, summarize, or translate highlighted text, and clicking a page number in a response jumps to that page. In the test, all five answers were correct and cited the correct pages.
Timeline
2024: Adobe began putting AI at the center of Acrobat's product offering.
November 14, 2026: An article describing the local AI setup was published.
Pricing Pressure
The local setup is an alternative to Adobe's AI Assistant, which is bundled into Acrobat Studio at $24.99 a month. Readers who want AI help with PDFs now have a route that avoids that recurring charge.
Readers who use PDFs for work or study can get AI summaries, translations, and page-referenced answers without an Adobe subscription, though the setup requires installing a local model and configuring SumatraPDF. The developer's tests suggest that highlighted-text handling depends on the SumatraPDF version in use.
The takeaway
Free AI features for PDFs are possible on a personal computer, but users should check which SumatraPDF version they run, since stable 3.6.1 limits highlighted text to about 1,000 characters.
Further reading
For more on how AI tools are reshaping everyday software, explore our Artificial Intelligence coverage.
Source note: This article includes information reported by XDA-Developers.
Live Poll
Would you pay a monthly subscription for AI features in your PDF reader?
