Bilingual PDF Translator EN

Bilingual PDF Translator is a lightweight, high-performance Microsoft Edge extension designed for researchers, software engineers, students, and professionals who need accurate, context-aware English-to-Vietnamese translation of PDF documents while preserving original visual layout and reading flow.

Using a synchronized dual-pane viewer, the extension displays the original English PDF side-by-side with translated Vietnamese text blocks, maintaining paragraph boundaries, headings, formulas, and references.

### Key Features

1. Synchronized Dual-Pane Viewer
Read original English PDF pages side-by-side with aligned Vietnamese translations. Features synchronized scrolling, block highlighting, zoom controls, and multi-mode views (Side-by-Side, Original Only, Translated Only).

2. Layout & Structure Preservation
Segments text blocks and paragraphs with PDF.js while maintaining 1:1 bidirectional mapping between source and translated blocks.

3. AI Translation via Google Gemini
Connect directly to Google Gemini models (Gemini 1.5 Flash, Gemini 1.5 Pro, Gemini 2.0 Flash) using your own API key.

4. Invariant Preservation
Numbers, units, mathematical formulas, URLs, and code snippets remain preserved verbatim.

5. Interactive Review & USER_EDITED Protection
Edit any translation in-place. Manually edited translations are permanently locked and protected against accidental overwrites by automatic re-translations or batch retries.

6. Local Persistence & Session Restore
Saves document structures, translations, and custom edits locally using IndexedDB and chrome.storage.local. Reopening tabs restores your work instantly.

7. Full Concurrency & Rate Limit Management
Configurable bounded concurrency (1–10 requests) with exponential backoff and instant cancellation.

8. Bring Your Own Key (BYOK)
Zero subscription fees and zero developer middleman servers. All translation requests travel directly from your browser to Google's official Gemini endpoint.

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### How It Works

1. Configure Your Key: Click the extension icon in Microsoft Edge and enter your Google Gemini API key.
2. Open a PDF: Open any online PDF document in Edge or upload a local PDF file into the viewer.
3. Translate: Click Translate Page to translate the visible page or Translate Doc for the entire document.
4. Read & Compare: Scroll through the document with synchronized dual-pane alignment.
5. Review & Custom Edit: Click on any translated block to edit text, mark items as Accepted/Rejected, and export your bilingual session to HTML, Markdown, Plain Text, or JSON.

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### Privacy & Bring Your Own Key (BYOK)

- Zero Telemetry: No tracking scripts, analytics libraries, or telemetry collection.
- Local Storage: Your Gemini API key and translation data are stored exclusively in your local browser profile.
- Direct Transmission: Text content is transmitted over secure HTTPS directly to Google Gemini API (generativelanguage.googleapis.com). No third-party proxy or developer relay is used.

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### Limitations & Considerations
- Scanned documents or image-only PDFs without an embedded OCR text layer cannot be parsed directly.
- Requires a valid Google Gemini API key obtained from Google AI Studio.