SimplePDF Copilot brings AI assistance to PDF editing, offering field filling, question answering, and page management capabilities. Built on the 7-year-old SimplePDF platform used by 200k+ monthly users, this tool represents a significant evolution in document interaction.

The system maintains strict privacy by keeping PDFs entirely within the browser. All parsing, rendering, and field detection happen client-side. The implementation uses client-side tool calling, where the LLM suggests actions but execution occurs locally, preventing document exposure.

Developed specifically for healthcare customers where document privacy is non-negotiable, Copilot addresses the critical need to avoid shipping PII to third parties. The stack includes Tanstack Start, Vercel's AI SDK, and Tailwind CSS, with the demo available on GitHub.

Client-side tool calling provides both performance benefits and enhanced privacy controls. By limiting data exposed to the LLM and executing tools locally, the system offers a privacy-preserving alternative to traditional PDF AI tools that often require document uploads to external servers.