# SIGNATURE PAD & PDF GENERATION DOCUMENTATION
Generated: 2025-09-06 12:10:03
Fixed by: [Your Name] on 2025-09-06

## PROBLEM DESCRIPTION
The signature pad feature in /contracts/<id>/sign was not working in production.
- SignaturePad.js captures signatures in the browser
- Backend converts signatures to PDF using xhtml2pdf
- Production failed with ImportError: No module named 'xhtml2pdf'

## ROOT CAUSE
xhtml2pdf was imported in app/services/pdf_service.py but missing from requirements.txt
This worked locally (where developer had manually installed it) but failed in production.

## SOLUTION
Added xhtml2pdf and its dependencies to requirements.txt:
- xhtml2pdf==0.2.11 (PDF generation from HTML)
- reportlab>=3.6.12 (PDF creation library, required by xhtml2pdf)
- Pillow>=10.0.0 (Image processing for embedding signatures)
- html5lib>=1.1 (HTML parsing, required by xhtml2pdf)

## FILES INVOLVED
- app/services/pdf_service.py - Uses xhtml2pdf for PDF generation
- app/templates/contracts/review.html - Contains signature pad UI
- app/routes.py - /contracts/<id>/sign endpoint
- requirements.txt - Added missing dependencies

## TESTING CHECKLIST
1. Local: Draw signature and submit on contract review page
2. Production: Test signature capture after deployment
3. Verify PDF generation with embedded signature
4. Check CDN loading of SignaturePad.js (requires internet)

## TROUBLESHOOTING
If signature pad not working:
- Check browser console for SignaturePad.js loading errors
- Verify CDN is accessible (https://cdn.jsdelivr.net)
- Check fly logs for ImportError related to xhtml2pdf
- Ensure all PDF dependencies installed: pip list | grep -E "xhtml2pdf|reportlab|Pillow"

## RELATED FEATURES
This fix enables:
- Digital contract signing
- PDF generation with embedded signatures
- Contract PDF downloads
- Invoice PDF generation (uses same service)