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ToolsThe story, in brief

Show HN: Filling PDF forms with AI using client-side tool calling

Not a pilot. SimplePDF Copilot lets you fill PDFs with AI—without ever sending your document to the cloud.

Reporting by Hacker News 2 min brief
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The KeyNews take

Why it matters

A developer shipped client-side tool calling for PDFs, solving a real privacy problem for healthcare teams. This is the emerging pattern: AI features that keep sensitive data in the browser, not in vendor clouds.

The key facts

17 to know

  1. SimplePDF Copilot: AI assistant for PDF field filling, form completion, and document manipulation

  2. All parsing, rendering, and field detection runs client-side—PDFs never leave the browser

  3. Built on SimplePDF, used by 200k+ monthly users, 7-year-old project

  4. Client-side tool calling via iframe postMessage architecture

  5. Privacy model: LLM sees only necessary text/messages; PII stays local

  6. Supports BYOK (bring your own key) and local LLM inference (tested with LM Studio)

  7. Default LLM: DeepSeek V4 Flash (demo proxy)

  8. Tech stack: Tanstack Start, Vercel AI SDK, Tailwind

  9. Open source demo on GitHub; SimplePDF core remains proprietary

  10. Solves healthcare compliance need for document privacy without third-party shipping

  11. SimplePDF Copilot: AI assistant for PDF form filling, field detection, page management—runs client-side

  12. 200k+ monthly users on SimplePDF base product (7-year-old privacy-first PDF editor)

  13. Client-side tool calling architecture: LLM intent + browser execution (speed + data containment)

  14. Supports bring-your-own-key (BYOK) to any cloud LLM or fully local inference (LM Studio tested)

  15. Default model: DeepSeek V4 Flash via demo proxy

  16. Tech stack: Tanstack Start, Vercel AI SDK, Tailwind; open-source demo on GitHub

  17. Use case: Healthcare/regulated industries where PII/PHI cannot leave the browser

Go to the source

Hacker Newscopilot.simplepdf.com

Publisher excerpt: Hey HN! I built SimplePDF Copilot: an AI assistant that can interact with the PDF editor. It fills fields, answers questions, focuses on a specific field, adds fields, deletes pages, and so on. It's built on top of SimplePDF that I started 7 years ago, pioneering privacy-respecting client-side pdf…
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