Pandoc Unicode Sanitization for PDF Conversion

Problem

LaTeX (used by pandoc for PDF output) may fail or produce errors when encountering non-ASCII Unicode characters like currency symbols (₹, €, £), special quotes, or other Unicode characters not supported by the default LaTeX engine.

Solution

Pre-process Markdown files to replace problematic Unicode characters with ASCII equivalents before running pandoc PDF conversion.

Steps

1. Identify Problematic Characters

Common problematic characters include:

• Currency symbols: ₹, €, £, ¥
• Special quotes: " " ' '
• Arrows: →, ←, ↑, ↓
• Bullets: •, ◦
• Other symbols: ©, ®, ™, ±, ×, ÷, —, –

2. Create a Sed Substitution Script

Create a shell script for reusable sanitization:

#!/bin/bash
# sanitize-for-pdf.sh

sed -e 's/₹/Rs/g' \
    -e 's/€/EUR/g' \
    -e 's/£/GBP/g' \
    -e 's/¥/JPY/g' \
    -e 's/"/"/g' \
    -e 's/"/"/g' \
    -e "s/'/'/g" \
    -e "s/'/'/g" \
    -e 's/→/->/g' \
    -e 's/←/<-/g' \
    -e 's/•/-/g' \
    -e 's/©/(c)/g' \
    -e 's/®/(R)/g' \
    -e 's/™/(TM)/g' \
    -e 's/±/+/ -/g' \
    -e 's/×/x/g' \
    -e 's/÷/\//g' \
    -e 's/—/--/g' \
    -e 's/–/-/g' \
    "$1"

3. Run Sanitization Before Pandoc

# Using the script
./sanitize-for-pdf.sh input.md > sanitized.md
pandoc sanitized.md -o output.pdf

# Or inline
cat input.md | sed 's/₹/Rs/g; s/€/EUR/g; s/£/GBP/g' | pandoc -o output.pdf

4. Alternative: Use iconv for Automatic Transliteration

For broader Unicode coverage:

iconv -f UTF-8 -t ASCII//TRANSLIT < input.md > sanitized.md
pandoc sanitized.md -o output.pdf

5. Alternative: Use XeLaTeX or LuaLaTeX Engine

If you want to preserve Unicode characters, use a Unicode-capable engine:

pandoc input.md -o output.pdf --pdf-engine=xelatex
# or
pandoc input.md -o output.pdf --pdf-engine=lualatex

Best Practices

• Sanitize files before conversion rather than debugging LaTeX errors after
• Keep a mapping of your organization's common symbols and preferred replacements
• Test with a small sample before processing large documents
• Consider using XeLaTeX/LuaLaTeX if Unicode preservation is required
• Document which characters cause issues in your specific environment

Common Error Signs

Look for these LaTeX errors that indicate Unicode issues:

• Package inputenc Error: Unicode character ... not set up

• LaTeX Error: Unicode character ... cannot be used with pdflatex

• Missing or garbled characters in the output PDF