nupdf

nupdf is a PDF engine for AI agents, in Rust: a command-line tool, an MCP server and a library, built to be called by a model rather than read by a person.

• Correct. Each subsystem is checked file by file against a pinned build of MuPDF, and parity is ratcheted in CI, so a file reads in nupdf as it reads in MuPDF.
• Safe. No unsafe code, no panics on input, explicit limits on every loop over a file’s contents, and continuous fuzzing. A hostile file can fail to open; it cannot crash or hang the agent that opened it.
• Parallel. A parsed document is shared across threads, so its pages are processed at once.
• Agent-first. Every command prints one versioned JSON report with stable ids for each span of text, diagnostics as data instead of log lines, budgets and cursors for long files, and a redaction that reads its own output back to prove nothing is left.

Who it is for

• Agents and the people who build them. An agent that gets a PDF (an invoice, a contract, a scanned form, a bundle of statements) can triage it, read it in reading order or by position, find text and get its boxes, render a page only when text cannot answer, fill forms, compare versions, and redact with a check that the redaction worked. Claude Code and MCP shows how to wire it in.
• Scripts and pipelines that want what is in a PDF as JSON, with exit codes that mean something (see the agent interface).
• Rust programs that want a memory-safe PDF reader and writer: see as a library.

Where to go next

• Install, then first commands.
• Results: what nupdf is measured to do, and where it falls short.
• Agent interface: the JSON contract every command follows.
• Architecture and decisions: how it is built and why.
• Security: how to report a vulnerability, and the threat model.

License

nupdf is licensed under the GNU Affero General Public License, version 3 or later (AGPL-3.0-or-later). It follows MuPDF’s design, algorithms and behavior closely enough to be a derivative work of MuPDF, by Artifex Software, Inc., and is distributed under MuPDF’s license. It is an independent project, not affiliated with or endorsed by Artifex. The NOTICE lists what nupdf derives from and the third-party code and data it includes, with their licenses.