PDF Translate

PDF Translate (English → Chinese)

This skill translates PDF documents using PDFMathTranslate-next (pdf2zh_next), the BabelDOC-based translator that preserves formulas, charts, table of contents, and page layout. It produces two files per input:

• *-mono.pdf — monolingual translated PDF (Chinese only)
• *-dual.pdf — bilingual PDF (original + translation, side by side or alternating)

Why this skill exists

Translating an academic PDF well requires preserving math, figures, and layout — something plain LLM translation can't do. pdf2zh_next handles that, but it has a non-trivial install (Python 3.12, model assets) and many engine options. This skill automates the environment setup and picks a translation engine that reuses credentials the user already has, so translation "just works" without manual configuration.

Workflow

Run the setup script first (installs pdf2zh_next if missing, verifies it), then the translate script (detects the best engine and runs the translation). Both scripts are idempotent.

Subsequent runs are fast. Once pdf2zh_next is installed and the model assets are downloaded (after the first successful translation), setup.sh becomes a silent sub-second no-op — it detects the install and the ~/.cache/babeldoc/models cache and returns immediately without spawning a Python import or re-downloading anything. Re-running it on every invocation is cheap and safe; you do not need to track whether setup has happened before.

Step 1 — Ensure the environment is ready

bash ~/.claude/skills/pdf-translate/scripts/setup.sh

This installs pdf2zh_next via uv tool install --python 3.12 pdf2zh-next (the project requires Python ≥3.10,<3.14; 3.12 is the documented recommendation) and confirms it is on PATH. It is fast and safe to re-run. The first real translation downloads layout/translation model assets (DocLayout-YOLO + fonts, hundreds of MB) into `/.cache/babeldoc/` — tell the user the first run is slow because of this one-time download. The setup and translate scripts detect this cache and skip the "slow first run" messaging once the models are present.

Step 2 — Translate

bash ~/.claude/skills/pdf-translate/scripts/translate.sh "<input.pdf>" [options]

The script auto-detects a translation engine:

1. ClaudeCode (default when claude CLI is available) — detects if the user is running from Claude Code by checking for the claude CLI on PATH. Uses the exact model Claude Code is configured to use (resolved via ANTHROPIC_DEFAULT_SONNET_MODEL, etc.). This is the default when working in Claude Code, so the translation uses the same model ecosystem the user is already in. Note: it spawns one claude -p subprocess per text segment, so it is slower than the OpenAI engine.
2. OpenAI-compatible (fallback when API key exists) — used when claude CLI is not found but OPENAI_API_KEY is set. Reuses the model configured for Codex: reads base_url + model from ~/.codex/config.toml and the API key from OPENAI_API_KEY. Fast (HTTP, high concurrency), ideal for full papers.
3. SiliconFlowFree (zero-config fallback) — used when neither claude CLI nor API key is detectable. The project's free GLM-4-9B service; needs no key. Note: file content is forwarded through the project maintainer's server.

Override detection with flags: --engine openai|siliconflowfree|claudecode, --model <name>, --base-url <url>, --api-key <key>.

Common options:

• --output <dir> — output directory (default: an output/ folder next to the input PDF)
• --pages "1-5,8" — translate only some pages
• --lang-in en --lang-out zh-CN — language codes (defaults: en → zh-CN)
• --qps N --pool-max-workers N — concurrency tuning (see references/advanced.md)
• --no-dual / --no-mono — suppress one of the two outputs
• Pass any other pdf2zh_next flag through with -- <flag> <value>

Step 3 — Report results

After the script finishes, it prints the paths of the generated *-mono.pdf and *-dual.pdf. Tell the user where these files are (relative to the input), open/preview them if asked, and note the engine + model that was used. If the user wants different quality or speed, suggest overrides (see references/advanced.md).

Default behavior choices (and how to change them)

• Source/target language: English → Simplified Chinese (en → zh-CN). Override with --lang-in / --lang-out. Full language code list is in references/advanced.md.
• Engine: ClaudeCode when claude CLI is on PATH (default in Claude Code), else OpenAI-compatible when a key is found, else SiliconFlowFree. Use --engine openai to force the OpenAI engine even from Claude Code. The claudecode engine reuses Claude Code's configured model; the OpenAI engine reuses the model named in ~/.codex/config.toml.
• Model: for the openai engine, the model from ~/.codex/config.toml; for claudecode, sonnet (resolved by Claude Code to the user's configured model). Reasoning models (e.g. gpt-5.5, glm-5.2) work but are slower and use more tokens; for large papers consider a lighter chat model via --model.
• Concurrency: modest defaults (--qps 10 --pool-max-workers 30 for the OpenAI engine; --qps 4 --pool-max-workers 8 for claudecode since each segment is a subprocess). Increase for faster translation if the gateway allows it.

When something goes wrong

• command not found: pdf2zh_next after install — the uv tool bin dir isn't on PATH. The scripts add ~/.local/bin to PATH themselves, but if the user runs pdf2zh_next directly in their own shell, they need export PATH="$HOME/.local/bin:$PATH" (Linux/macOS).
• First translation hangs on "loading assets" / downloading — normal one-time model download. Wait it out.
• 429 / rate-limit errors — lower --qps and --pool-max-workers.
• Gateway returns errors for the OpenAI engine — the detected base_url may only expose the responses API, not chat-completions. Run with --engine siliconflowfree to bypass, or point --base-url at a chat-completions endpoint.
• Out-of-memory / very large PDFs — use --pages to translate in chunks, or --max-pages-per-part 50.

For the full option reference, engine configuration details, translating to other languages, glossaries, and offline/air-gapped usage, read references/advanced.md.