---
name: pdf-extraction-fallbacks-8fd00e9806da
description: Multi-fallback PDF/text extraction with early failure detection and sequential tool fallbacks
---

# PDF Extraction with Multi-Fallback Strategy

## Purpose

When extracting text from PDFs (especially regulatory documents, handbooks, or protected content), single-method approaches often fail due to JavaScript protection, CORS restrictions, encoding issues, or corrupted downloads. This skill provides a robust multi-fallback workflow that detects failures early and tries sequential extraction methods.

## Core Pattern

1. **Download with validation** - Check file size and content sanity immediately
2. **Sequential extraction attempts** - Try multiple tools in order of reliability
3. **Early failure detection** - Don't proceed with obviously corrupt files
4. **Document fallback path** - Log which method succeeded for future reference

## Step-by-Step Instructions

### Step 1: Download and Validate

Before attempting extraction, validate the downloaded file:

```bash
# Download the PDF
curl -L -o document.pdf "$URL"

# Check file size (reject if < 1KB - likely error page)
FILE_SIZE=$(stat -f%z document.pdf 2>/dev/null || stat -c%s document.pdf 2>/dev/null)
if [ "$FILE_SIZE" -lt 1024 ]; then
    echo "ERROR: File too small ($FILE_SIZE bytes) - likely not a valid PDF"
    # Check if it's an HTML error page
    head -c 200 document.pdf | grep -i "<html\|<!doctype\|error\|access denied" && \
        echo "Detected HTML error page instead of PDF"
    exit 1
fi

# Check PDF magic bytes
HEAD_BYTES=$(head -c 4 document.pdf)
if [ "$HEAD_BYTES" != "%PDF" ]; then
    echo "ERROR: File does not start with PDF magic bytes"
    head -c 100 document.pdf
    exit 1
fi
```

### Step 2: Primary Extraction (pdftotext)

```bash
# Try pdftotext first (fastest, most reliable for simple PDFs)
if command -v pdftotext &> /dev/null; then
    pdftotext -layout document.pdf output.txt 2>/dev/null
    if [ -s output.txt ]; then
        WORD_COUNT=$(wc -w < output.txt)
        if [ "$WORD_COUNT" -gt 50 ]; then
            echo "SUCCESS: pdftotext extracted $WORD_COUNT words"
            exit 0
        fi
    fi
fi
```

### Step 3: Fallback 1 (PyMuPDF/fitz)

```python
# Try PyMuPDF - handles more complex PDFs
import fitz  # pymupdf

try:
    doc = fitz.open("document.pdf")
    text = ""
    for page in doc:
        text += page.get_text()
    
    if len(text.strip()) > 500:  # Sanity check
        with open("output.txt", "w") as f:
            f.write(text)
        print(f"SUCCESS: PyMuPDF extracted {len(text)} characters")
    else:
        print("WARNING: PyMuPDF extraction too short, trying next method")
except Exception as e:
    print(f"PyMuPDF failed: {e}")
```

### Step 4: Fallback 2 (pdfplumber)

```python
# Try pdfplumber - better for tables and structured content
import pdfplumber

try:
    text = ""
    with pdfplumber.open("document.pdf") as pdf:
        for page in pdf.pages:
            page_text = page.extract_text()
            if page_text:
                text += page_text + "\n"
    
    if len(text.strip()) > 500:
        with open("output.txt", "w") as f:
            f.write(text)
        print(f"SUCCESS: pdfplumber extracted {len(text)} characters")
    else:
        print("WARNING: pdfplumber extraction too short")
except Exception as e:
    print(f"pdfplumber failed: {e}")
```

### Step 5: Handle JavaScript-Protected Pages

If all methods fail, the PDF may be JavaScript-protected:

```python
# Check for JavaScript in PDF
import fitz

doc = fitz.open("document.pdf")
has_js = False
for page in doc:
    if page.get_java_script():
        has_js = True
        break

if has_js:
    print("WARNING: PDF contains JavaScript - may be protected")
    # Try rendering pages as images and OCR (requires additional tools)
    # Or try alternative download source
```

### Step 6: Alternative Sources

If the primary URL fails:
- Try alternative domains (e.g., `.gov` mirrors, archive.org)
- Check if the document is available via API
- Look for HTML version of the same content
- Search for the document title + "pdf" to find mirrors

## Decision Tree

```
Download PDF
    │
    ├─→ File < 1KB? → REJECT (likely error page)
    ├─→ No %PDF header? → REJECT (not a PDF)
    │
    └─→ Valid PDF
         │
         ├─→ pdftotext → >50 words? → SUCCESS
         │              └─→ Try next
         │
         ├─→ PyMuPDF → >500 chars? → SUCCESS
         │             └─→ Try next
         │
         ├─→ pdfplumber → >500 chars? → SUCCESS
         │                 └─→ Try next
         │
         └─→ All failed → Check for JS protection, try alternative sources
```

## Common Failure Modes

| Symptom | Likely Cause | Solution |
|---------|-------------|----------|
| File < 100 bytes | JavaScript error page | Check CORS, try different user-agent |
| File ~1-5KB | HTML error/warning page | Parse HTML for actual PDF link |
| pdftotext returns empty | Encrypted/protected PDF | Try PyMuPDF with password handling |
| Garbled text output | Encoding issue | Try pdfplumber, specify encoding |
| Extraction very short | Images-only PDF | Need OCR (tesseract) |

## Example Complete Workflow Script

Save as `extract_pdf_robust.sh`:

```bash
#!/bin/bash
set -e

URL="$1"
OUTPUT="${2:-output.txt}"
TEMP_PDF="temp_download.pdf"

echo "Downloading from: $URL"
curl -L -A "Mozilla/5.0" -o "$TEMP_PDF" "$URL"

# Validate
SIZE=$(stat -c%s "$TEMP_PDF" 2>/dev/null || stat -f%z "$TEMP_PDF")
echo "Downloaded: $SIZE bytes"

if [ "$SIZE" -lt 1024 ]; then
    echo "ERROR: File too small - checking content..."
    head -200 "$TEMP_PDF"
    exit 1
fi

if ! head -c 4 "$TEMP_PDF" | grep -q "%PDF"; then
    echo "ERROR: Not a valid PDF file"
    head -100 "$TEMP_PDF"
    exit 1
fi

# Try extraction methods
python3 << 'PYTHON'
import sys
import fitz
import pdfplumber

pdf_path = "temp_download.pdf"
output_path = "output.txt"

# Method 1: PyMuPDF
try:
    doc = fitz.open(pdf_path)
    text = "".join(page.get_text() for page in doc)
    if len(text.strip()) > 500:
        with open(output_path, "w") as f:
            f.write(text)
        print(f"PyMuPDF: {len(text)} chars")
        sys.exit(0)
except Exception as e:
    print(f"PyMuPDF failed: {e}")

# Method 2: pdfplumber
try:
    text = ""
    with pdfplumber.open(pdf_path) as pdf:
        for page in pdf.pages:
            txt = page.extract_text()
            if txt:
                text += txt + "\n"
    if len(text.strip()) > 500:
        with open(output_path, "w") as f:
            f.write(text)
        print(f"pdfplumber: {len(text)} chars")
        sys.exit(0)
except Exception as e:
    print(f"pdfplumber failed: {e}")

print("All extraction methods failed")
sys.exit(1)
PYTHON
```

## Best Practices

1. **Always validate** - Never assume a download succeeded
2. **Log the path taken** - Record which method worked for debugging
3. **Set reasonable thresholds** - 50 words / 500 chars minimum for "success"
4. **Keep raw PDF** - Don't delete the original until extraction is confirmed
5. **Retry with variations** - Different user-agents, referer headers, or mirrors

## Dependencies

- `curl` - For downloading
- `poppler-utils` (pdftotext) - Optional, fast extraction
- `PyMuPDF` (`fitz`) - `pip install pymupdf`
- `pdfplumber` - `pip install pdfplumber`

---
Source attribution: AG064
Original project: https://github.com/AG064/OpenSpace/blob/ff671ef61ed6587c49bd54c81cdc751c0b99e363/gdpval_bench/skills/pdf-extraction-fallbacks/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2026 ✨Data Intelligence Lab@HKU✨

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: AG064
Original project: https://github.com/AG064/OpenSpace/blob/ff671ef61ed6587c49bd54c81cdc751c0b99e363/gdpval_bench/skills/pdf-extraction-fallbacks/SKILL.md
Attribution basis: Source repository record

Fields of work: Data & Analytics, Development & Engineering
Roles: Backend Developer, Data Analyst, ML / AI Engineer
Specialties: API, Backend
Tools: Pdfplumber, Pdftotext, Pymupdf
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 2e8f40cd03ec00ff40b5f44a7d77544255934c3949863a7d2ad520555311b8dc