PDF Translation Skill

Translate PDF documents between any language pair with optimized support for academic papers and documents with complex layouts.

When to Use This Skill

Use this skill when:

• User wants to translate a PDF document to another language
• User has academic papers, research documents, or technical manuals to translate
• User needs to preserve document structure (tables, headings, lists) during translation
• User wants both Markdown and PDF output formats
• User mentions translating documents with tables, figures, or complex layouts

Usage

/pdf-translator <pdf_path> [options]

Arguments

• <pdf_path>: PDF file or directory containing PDFs

Options

Option	Description	Default
--source-lang	Source language code (auto for detection)	auto
--target-lang	Target language code	ko
--output-format	Output format (markdown/pdf/both)	both
--output-dir	Output directory	./translated
--parallel	Concurrent agents	5
--dict	Custom dictionary (JSON)	none
--high-quality	Prefer the runtime's stronger model for translation	false
--academic	Academic document mode	false
--term-style	Term annotation style (parenthesis/footnote/inline)	parenthesis
--first-occurrence	Annotate terms only on first occurrence	true
--describe-images	Add AI-generated image descriptions	false

Language Codes

ja (Japanese), en (English), ko (Korean), zh (Chinese), es (Spanish), fr (French), de (German), ru (Russian), ar (Arabic), he (Hebrew), or any ISO 639-1 code.

Examples

# Basic translation (English PDF to Korean)
/pdf-translator "/docs/manual.pdf"

# Japanese academic paper to Korean with terminology annotations
/pdf-translator "/papers/research.pdf" --source-lang ja --academic

# High-quality translation using the runtime's stronger model
/pdf-translator "/papers/important.pdf" --high-quality

# Academic mode with footnote-style term annotations
/pdf-translator "/papers/thesis.pdf" --academic --term-style footnote

# Batch translation of a directory
/pdf-translator "/docs/" --target-lang ko --parallel 10

# Markdown output only
/pdf-translator "/books/novel.pdf" --output-format markdown

# Arabic RTL document to English
/pdf-translator "/docs/arabic.pdf" --source-lang ar --target-lang en

---

Architecture

flowchart LR
    PDF[PDF] --> Extract[extract_to_markdown.py]
    Extract --> Source[source.md + images/]
    Source --> Split[split_markdown.py]
    Split --> Sections[sections/]
    Sections --> Translate[Translator Agents]
    Translate --> Merged[translated.md]
    Merged --> GenPDF[generate_pdf.py]
    GenPDF --> Output[translated.pdf]

Key Features:

• Full document context preserved during translation
• Clean Markdown intermediate format (human-readable, editable)
• Section-based parallel translation for large documents
• pandoc + weasyprint for high-quality PDF output

---

Execution Workflow

Phase 0: Environment Setup

bash scripts/setup_env.sh

This installs pandoc and creates .venv/ with Python dependencies (pymupdf, pdfplumber, weasyprint).

PYTHON=".venv/bin/python"

Phase 1: Extract PDF to Markdown

WORK_DIR="/tmp/pdf_translate_$(date +%s)"
$PYTHON scripts/extract_to_markdown.py \
  --pdf "{PDF_PATH}" \
  --output-dir "$WORK_DIR" \
  --source-lang en \
  --target-lang ko

Output:

• $WORK_DIR/source.md - Original Markdown (preserves structure)
• $WORK_DIR/images/ - Extracted images
• $WORK_DIR/metadata.json - Document metadata

Phase 2: Split Markdown (if needed)

For large documents (>6000 tokens), split into sections:

$PYTHON scripts/split_markdown.py \
  --input "$WORK_DIR/source.md" \
  --output-dir "$WORK_DIR/sections" \
  --max-tokens 6000

Output:

• $WORK_DIR/sections/section_001.md
• $WORK_DIR/sections/section_002.md
• $WORK_DIR/sections/sections_manifest.json

Phase 3: Translation

Translate each section using the Markdown translator guide (references/translator_markdown.md).

Option A: Direct Translation (Small documents)

The orchestrator translates the Markdown directly:

1. Read source.md (or each section)
2. Translate following translator_markdown.md guidelines
3. Write to translated.md

Option B: Parallel Translation (Large documents)

Dispatch translation work for each section. Use parallel agents if the active runtime supports them; otherwise process sections sequentially:

Translation job:
  prompt: "Read references/translator_markdown.md for guidelines.
           Translate $WORK_DIR/sections/section_001.md from English to Korean.
           Write output to $WORK_DIR/translated/section_001.md"

Phase 4: Merge Translated Sections

If split, merge translated sections:

cat $WORK_DIR/translated/section_*.md > $WORK_DIR/translated.md

Phase 5: Generate PDF

$PYTHON scripts/generate_pdf.py \
  --markdown "$WORK_DIR/translated.md" \
  --output "$OUTPUT_DIR/{filename}_translated.pdf"

Phase 6: Validation (Optional)

Review output for:

• Markdown formatting preserved
• Tables rendered correctly
• Images referenced properly
• No untranslated text

---

Model Selection

Default (no flags)

Task	Model
Markdown translation	Standard translation-capable model
Validation	Fast model

With --high-quality

Task	Model
Markdown translation	Strongest practical model
Validation	Stronger model

---

Academic Mode (--academic)

When enabled:

• Technical terms include original language in parentheses
• Abbreviations expanded on first occurrence
• Citations and references preserved
• Formal academic writing style maintained

Term Annotation Styles (--term-style)

Style	Example
parenthesis	기계 학습(Machine Learning)
footnote	기계 학습¹
inline	기계 학습/Machine Learning

First Occurrence (--first-occurrence)

When true (default):

• First mention: 기계 학습(Machine Learning)
• Subsequent: 기계 학습

When false:

• All mentions include original term

---

Language-Specific Processing

Source	Special Handling
Japanese	Vertical→horizontal writing, ruby tag removal
Chinese	Traditional/simplified handling, vertical→horizontal
Arabic/Hebrew	RTL→LTR conversion, text direction adjustment
English	Standard processing

Target	Special Handling
Korean	Translationese removal, natural expression check

---

Custom Dictionary (Optional)

The translator works without external dictionary files. It naturally translates based on context.

Use custom dictionaries ONLY for:

• Proper nouns: names, places, organizations, brands
• Document-specific terms: proprietary terms unique to this document

Do NOT add common words - let the translator handle them naturally.

Creating a Custom Dictionary

Use the --dict option with a JSON file:

{
  "metadata": {
    "source_language": "en",
    "target_language": "ko",
    "document_title": "Annual Report 2024"
  },
  "proper_nouns": {
    "names": { "John Smith": "존 스미스" },
    "places": { "Silicon Valley": "실리콘밸리" },
    "organizations": { "OpenAI": "OpenAI" }
  },
  "domain_terms": {
    "ProprietaryTech": "고유 기술명"
  },
  "preserve_original": {
    "terms": ["API", "GPU", "URL"]
  },
  "abbreviations": {
    "LLM": "Large Language Model"
  },
  "style_notes": {
    "notes": ""
  }
}

Templates

Template	Use Case
assets/template.json	General documents
assets/template_academic.json	Academic papers, technical documents

---

Work Directory Structure

$WORK_DIR/
├── source.md               # Original Markdown (extracted from PDF)
├── metadata.json           # Document metadata (title, pages, languages)
├── images/                 # Extracted images
│   ├── page001_img000.png
│   ├── page002_img000.png
│   └── ...
├── sections/               # Split sections (for large documents)
│   ├── section_001.md
│   ├── section_002.md
│   └── sections_manifest.json
├── translated/             # Translated sections
│   ├── section_001.md
│   ├── section_002.md
│   └── ...
└── translated.md           # Final merged translation

---

Error Handling

Error	Action
PDF extraction failure	Skip corrupted file, report
Translation timeout	Retry with smaller chunks
Table extraction failure	Treat as text block
Layout preservation failure	Fallback to Markdown only
Low quality score	Re-translate with a stronger model

---

Text Processing

The following automatic text cleanup is applied during extraction and output generation:

Issue	Fix Applied
Corrupted characters (●)	Restored to parentheses
Broken URLs (spaces)	Spaces removed, domains fixed
Missing @ in emails	Restored based on pattern
Artifact text (a1111111111)	Filtered out
Small images (logos, icons)	Filtered (min 200x100)
Page headers/footers	Auto-detected and removed
Superscript numbers	Converted to ^[n] format
Reference section	Auto-formatted with merged entries
Concatenated words	Split using wordninja (thepatient → the patient)
Reversed text	Detected and corrected (rewol → lower)
Missing punctuation spaces	Added (text.Next → text. Next)
Table text spacing	Improved with x_tolerance parameter

PDF Extraction Error Correction

Some complex PDF artifacts cannot be fully corrected during extraction. The translator prompts include instructions to recognize and correct remaining errors:

• Split medical/scientific terms: broncho alveolar → bronchoalveolar
• Single-letter fragments: Diaphragm a tic → Diaphragmatic

See references/translator_markdown.md and references/translator_academic.md for details.

Header/Footer Detection

Automatically detects and removes common header/footer patterns:

• DOI links (https://doi.org/...)
• Journal volume/issue patterns (Journal| (2024) 16:642)
• Page numbers (standalone numbers at page boundaries)
• Date stamps (Received: 23 July 2024)
• Copyright notices

Superscript Handling

Reference numbers and author affiliations are detected by font size and converted to standard format:

• word¹ → word^[1]
• Author¹,² → Author^[1,2]

Reference Section Processing

Multi-language support for reference section headers:

• English: References, Bibliography, Works Cited
• Korean: 참고문헌
• German: Literatur, Literaturverzeichnis
• French: Références, Bibliographie
• Chinese/Japanese: 参考文献

List Detection

Automatically detects and formats various list styles:

• Bullet: •, ·, -, *, ▪, ▸, ►
• Numbered: 1., 1), (1), ①
• Roman: i., ii., iii.
• Letter: a., a), (a)

---

Output Formats

Markdown Output

• Preserves document structure (headings, paragraphs, lists)
• Tables converted to Markdown tables
• URLs converted to clickable links
• Metadata in YAML frontmatter

PDF Output

• Generated via pandoc + weasyprint from Markdown
• Clean text rendering with system fonts (Pretendard preferred)
• Proper table rendering with borders and headers
• Clickable links with styling
• Page numbers at bottom

---

File Reference

Path	Description
SKILL.md	This file
references/orchestrator.md	Orchestrator workflow guide
references/translator_markdown.md	Markdown translation guidelines
references/translator_academic.md	Academic document translation
references/validator_generic.md	Generic validation instruction
references/validator_ko.md	Korean-specific validation
scripts/setup_env.sh	Environment setup (installs pandoc, Python dependencies)
scripts/extract_to_markdown.py	PDF extraction to Markdown with images
scripts/split_markdown.py	Split large Markdown into sections by token count
scripts/generate_pdf.py	PDF output generation (Markdown → PDF via pandoc + weasyprint)
assets/template.json	Dictionary template for general documents
assets/template_academic.json	Dictionary template for academic documents

---

Known Limitations

PDF extraction has inherent limitations due to the format's nature:

Limitation	Description	Workaround
Figure text extraction	Text inside charts/graphs/diagrams may be extracted as body text	Manual review of figure areas
Complex table structures	Tables with merged cells or nested structures may not parse correctly	Tables extracted as best-effort Markdown
Multi-column layouts	Two-column academic papers may have text order issues	Usually handled correctly, but verify flow
Scanned PDFs	Image-based PDFs require OCR (not included)	Use OCR tools first, then translate
Mathematical formulas	LaTeX/MathML may not render perfectly	Formulas preserved as-is when possible

Quality Expectations

• Academic papers: 85-95% accuracy on text extraction
• Technical manuals: 80-90% accuracy
• Complex layouts: 70-85% accuracy (flowcharts, multi-column)
• Tables: Variable (depends on structure complexity)

For best results with complex documents, review the extracted source.md before translation and manually correct any extraction errors.