## MODIFIED Requirements

### Requirement: Enhanced PDF Export with Layout Preservation

The PDF export SHALL accurately preserve document layout from both OCR and direct extraction tracks with correct coordinate transformation and multi-page support. For Direct Track, a background image rendering approach SHALL be used for visual fidelity.

#### Scenario: Export PDF from direct extraction track
- **WHEN** exporting PDF from a direct-extraction processed document
- **THEN** the system SHALL render source PDF pages as full-page background images at 2x resolution
- **AND** overlay invisible text elements using PDF Text Rendering Mode 3
- **AND** text SHALL remain selectable and searchable despite being invisible
- **AND** visual output SHALL match source document exactly

#### Scenario: Export PDF from OCR track with full structure
- **WHEN** exporting PDF from OCR-processed document
- **THEN** the PDF SHALL use all 23 PP-StructureV3 element types
- **AND** render tables with proper cell boundaries
- **AND** maintain reading order from parsing_res_list

#### Scenario: Handle coordinate transformations correctly
- **WHEN** generating PDF from UnifiedDocument
- **THEN** system SHALL use explicit page dimensions from OCR results (not inferred from bounding boxes)
- **AND** correctly transform Y-axis coordinates from top-left (OCR) to bottom-left (PDF/ReportLab) origin
- **AND** prevent vertical flipping or position misalignment errors

#### Scenario: Direct Track PDF file size increase
- **WHEN** generating Layout PDF for Direct Track documents
- **THEN** the system SHALL accept increased file size due to embedded page images
- **AND** approximately 1-2 MB per page at 2x resolution is expected
- **AND** this trade-off is accepted for improved visual fidelity

#### Scenario: Chart elements excluded from text layer
- **WHEN** generating Layout PDF containing charts
- **THEN** the system SHALL NOT include chart-internal text in the invisible text layer
- **AND** chart visuals SHALL be preserved in the background image
- **AND** chart text SHALL NOT be available for text selection or translation