PDF Parser Light

A modern, lightweight desktop and command-line application for transcribing PDF files into Markdown/text (incl. LaTeX equations and HTML tables) using the generous free tier of Google Gemini API. Built with Python, CustomTkinter, and automated cross-platform PyInstaller packaging.

Features

• High-Fidelity Document Extraction: Transcribes dense document layouts, preserving formatting, converting equations into LaTeX, and structuring tabular data into HTML or Markdown tables without skipping or summarizing content.
• Modern Desktop GUI: Sleek CustomTkinter interface with asynchronous progress tracking, clipboard copy, and file saving (.md / .txt).
• Stateless CLI & Batch Mode: Command-line tool supporting single file parsing and batch directory processing with pacing and error handling.
• Smart PDF Chunking: Automatically splits large PDFs (>20 pages) into smaller page chunks to fit within context windows and handle extensive multi-page documents seamlessly.
• Daily Quota & Rate Limit Protection: Tracks daily free tier requests locally (20 free requests/day default for primary Flash models) with automatic fallback to high-capacity Flash Lite models (up to 500 requests/day per model) and exponential backoff retry loops on HTTP 429 rate limits.
• Mid-Chunk Recovery: Recovers partial transcriptions if processing fails mid-way through a large document.
• Zero-Cost & Direct API Access: Connects directly to Gemini API with no middleman SaaS markups, per-page fees, or paid subscription requirements.
• Local Key Storage: Saves Gemini API keys locally in platform-specific configuration directories (0o600 file permissions on POSIX systems; standard user directory on Windows).
• Cross-Platform: Executables for macOS, Windows, and Linux.

Why PDF Parser Light?

Many commercial document parsers, math OCR tools, and cloud document APIs impose paywalls, subscription models, or per-page processing fees. PDF Parser Light provides a powerful, cost-effective alternative by connecting your device directly to Google Gemini's vision models:

• Zero API Markup or Subscription Fees: No third-party SaaS middleman, cloud proxy, or monthly software fees. The app runs completely on your local hardware using your standard API key.
• Leverages Free Tier Quotas: Utilizes Google Gemini's generous free daily tier (ranging from 20 requests/day for primary Flash models up to 500+ requests/day across Flash Lite models), enabling hundreds of document pages to be transcribed daily at $0 cost.
• Multimodal LLM Power vs. Legacy OCR: Traditional OCR software struggles with complex math formulas, multi-column tables, and document hierarchy. Gemini's multimodal vision model extracts inline/block LaTeX equations and structured HTML/Markdown tables with high contextual accuracy in a single pass.

Downloads & Installation

Pre-built standalone executables can be downloaded from the Releases page.

1. Select your Operating System:
   • macOS: Download pdf-parser-light-macos.zip, extract it, and move PDF Parser Light.app to your /Applications folder.
   • Windows: Download pdf-parser-light-windows.zip, extract it, and launch PDF Parser Light.exe.
   • Linux: Download pdf-parser-light-linux.tar.gz, extract it, and run PDF Parser Light. (Note: Minimal distributions may require Tcl/Tk libraries via sudo apt install python3-tk).

Opening Unsigned Binaries (Security Prompts)

Because standalone releases are built via CI without commercial developer certificates, your OS may present security warnings on first launch:

• macOS (Gatekeeper):
  • Option 1 (Finder / System Settings): Control-Click (or Right-Click) PDF Parser Light.app, select Open, and click Open. On macOS Sequoia (15+), go to System Settings → Privacy & Security, scroll down to the Security section, and click Open Anyway.
  • Option 2 (Terminal Command): Strip the download quarantine attribute directly:

    xattr -d com.apple.quarantine "/Applications/PDF Parser Light.app"
    

• Windows (SmartScreen): Click More info, then click Run anyway.

Usage Guide

Desktop Application (GUI)

1. Launch PDF Parser Light.
2. Enter your Gemini API Key from https://aistudio.google.com/api-keys. Check "Remember API Key" to save it locally for future sessions.
3. Drag & drop a PDF file onto the window, or click Browse to choose a PDF file.
4. Click Process. The live console log and progress bar will indicate status.
5. Save the output as Markdown (.md) or plain text (.txt), or click Copy to Clipboard.

Command Line Interface (CLI)

Install in editable mode or run directly.

[!TIP] Recommended Workflow: Setting the GEMINI_API_KEY environment variable is the standard and recommended workflow for CLI usage. While --api-key KEY is available as a CLI flag, passing keys on the command line can expose them in shell command history (.bash_history / .zsh_history) and process listings (ps, Task Manager).

# Set your Gemini API Key in the environment (Recommended)
export GEMINI_API_KEY="your_api_key_here"

# Process a single PDF file
pdf-parser-light /path/to/document.pdf --output ./output.md

# Batch process an entire directory of PDFs
pdf-parser-light /path/to/pdf_folder/ --output ./markdown_output/

# Check remaining free requests for today
pdf-parser-light --usage

# Reset local daily free quota tracker
pdf-parser-light --reset-quota

# Force processing ignoring remaining daily quota
pdf-parser-light /path/to/document.pdf --force

# Process a specific page range
pdf-parser-light document.pdf --pages 1-50

# Resume parsing from a previous partial output file
pdf-parser-light document.pdf --resume

# Provide custom transcription instructions
pdf-parser-light document.pdf --prompt "Transcribe equations only into LaTeX."

CLI Command Options

Daily Quotas & Rate Limits

• Primary Free Tier Quota: Defaults to tracking 20 free Gemini 3.5 Flash requests/day locally, matching Google's standard free tier limit (configurable via GEMINI_FREE_LIMIT environment variable).
• High-Capacity Flash Lite Fallbacks: Google AI Studio provides significantly higher free tier limits for Flash Lite models (gemini-3.5-flash-lite, gemini-3.1-flash-lite) at up to 500 requests/day per model. Once the 20 primary request limit is reached, the app seamlessly cascades to Flash Lite models.
• Quota Warnings: Both GUI and CLI prompt/warn if a multi-chunk document requires more requests than remain in your primary daily quota, allowing seamless fallback execution.
• Model Fallback Chain: Tries primary Flash models first (gemini-3.6-flash, gemini-3.5-flash), then cascades to Lite fallbacks (gemini-3.5-flash-lite, gemini-3.1-flash-lite). High-demand errors (HTTP 503 / UNAVAILABLE / overloaded) switch to the next model immediately.
• Automatic Retries: Retries up to 3 times with exponential backoff on HTTP 429 rate limits or transient failures on the same model before falling back.

Privacy & Security

• Data Flow: Selected PDF files are uploaded temporarily to Google Gemini storage using the official google-genai SDK for model inference.
• Data Sensitivity & Privacy Notice: Do not upload sensitive, confidential, or copyrighted documents. Content is processed on Google servers in accordance with Google Gemini API terms and retention policies.
• Best-Effort Upload Cleanup: Uploaded files are deleted from Gemini API storage on a best-effort basis after transcription completes or during normal application cleanup. Deletion failures (e.g. network/API interruptions) or unexpected process crashes may leave temporary files stored until standard Google Gemini retention limits expire.
• Local Key Storage: API keys saved via the GUI are stored locally as plain text in user configuration files (~/Library/Application Support/pdf_parser_light/ on macOS, %LOCALAPPDATA%\pdf_parser_light\ on Windows, ~/.config/pdf_parser_light/ on Linux) with 0o700 directory and 0o600 file permissions on POSIX systems. On Windows, files are stored within the user profile directory without OS ACL enforcement.

Architecture & Workflow

flowchart TD
    A["PDF Input (File or Directory)"] --> B{"Input Interface"}
    B -->|"Desktop App"| C["CustomTkinter GUI"]
    B -->|"Terminal"| D["Stateless CLI / Batch Options"]

    C & D --> E["PDF Validation & Page Selection"]
    E --> F{"Page Count > 20?"}
    F -->|"Yes"| G["Smart Chunking (20 pages / chunk)"]
    F -->|"No"| H["Single Chunk Processing"]

    G & H --> I["Daily Quota & Rate Limit Check"]
    I --> J{"Quota Available?"}
    J -->|"Yes / --force"| K["Upload to Gemini API"]
    J -->|"Exceeded"| L["Quota Error / Fallback Models"]

    K --> M{"API Response"}
    M -->|"Success"| N["Extract & Append Transcribed Markdown"]
    M -->|"Rate Limit / Overloaded"| O["Exponential Backoff & Model Fallback"]
    O --> K

    N --> P["Best-Effort File Cleanup"]
    P --> Q["Save Output (.md / .txt) & Support Resuming"]

Developer Guide: Building from Source

Requirements

• Python 3.9+

Setup & Testing

# Clone repository
git clone https://github.com/jtaroreh/pdf-parser-light.git
cd pdf-parser-light

# Setup virtual environment and dependencies
python3 -m venv venv
source venv/bin/activate
pip install -e ".[test]"

# Run complete unit test suite
pytest -v

Building macOS App Bundle

Run the portable PyInstaller build script:

chmod +x build.sh
./build.sh

The output bundle will be located at dist/PDF Parser Light.app.