## ADDED Requirements

### Requirement: Translated PDF Generation

The system SHALL support generating PDF files with translated content while preserving the original document layout.

#### Scenario: Generate translated PDF from Direct track document
- **GIVEN** a completed translation for a Direct track processed document
- **WHEN** user requests translated PDF via `POST /api/v2/translate/{task_id}/pdf?lang={target_lang}`
- **THEN** the system loads the translation JSON file
- **AND** merges translations with UnifiedDocument by element_id
- **AND** generates PDF with translated text at original positions
- **AND** returns PDF file with Content-Type `application/pdf`

#### Scenario: Generate translated PDF from OCR track document
- **GIVEN** a completed translation for an OCR track processed document
- **WHEN** user requests translated PDF
- **THEN** the system generates PDF preserving all OCR layout information
- **AND** replaces original text with translated content
- **AND** maintains table structure with translated cell content

#### Scenario: Handle missing translations gracefully
- **GIVEN** a translation JSON missing some element_id entries
- **WHEN** generating translated PDF
- **THEN** the system uses original content for missing translations
- **AND** logs warning for each fallback
- **AND** completes PDF generation successfully

#### Scenario: Translated PDF for incomplete translation
- **GIVEN** a task with translation status "pending" or "translating"
- **WHEN** user requests translated PDF
- **THEN** the system returns 400 Bad Request
- **AND** includes error message indicating translation not complete

#### Scenario: Translated PDF for non-existent translation
- **GIVEN** a task that has not been translated to requested language
- **WHEN** user requests translated PDF with `lang=fr`
- **THEN** the system returns 404 Not Found
- **AND** includes error message indicating no translation for language

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### Requirement: Translation Merge Service

The system SHALL provide a service to merge translation data with UnifiedDocument.

#### Scenario: Merge text element translations
- **GIVEN** a UnifiedDocument with text elements
- **AND** a translation JSON with matching element_ids
- **WHEN** applying translations
- **THEN** the system replaces content field for each matched element
- **AND** preserves all other element properties (bounding_box, style_info, etc.)

#### Scenario: Merge table cell translations
- **GIVEN** a UnifiedDocument containing table elements
- **AND** a translation JSON with table_cell translations like:
  ```json
  {
    "table_1_0": {
      "cells": [{"row": 0, "col": 0, "content": "Translated"}]
    }
  }
  ```
- **WHEN** applying translations
- **THEN** the system updates cell content at matching row/col positions
- **AND** preserves cell structure and styling

#### Scenario: Non-destructive merge operation
- **GIVEN** a UnifiedDocument
- **WHEN** applying translations
- **THEN** the system creates a modified copy
- **AND** original UnifiedDocument remains unchanged
