PurifyPDF – A Privacy-First PDF Sanitizer in Your Inbox

This is a submission for the Postmark Challenge: Inbox Innovators.

What I Built

PurifyPDF is a privacy-first document sanitizer that lives in your inbox. Users simply email a PDF to [e-mail], and moments later receive a cleaned version — stripped of hidden metadata, embedded scripts, and potentially unsafe content.

There’s no app to install, no interface to learn — just send, wait, receive.

PurifyPDF does not retain files longer than necessary. Uploaded documents are stored temporarily for processing and purged after the retention period. User metadata is stored only for usage tracking and verification.

The service prioritizes security by design: PDFs are converted into image-only documents before being rebuilt, ensuring that any embedded scripts, file attachments, hyperlinks, or other potentially harmful elements are completely removed.

PurifyPDF is ideal for:

• Privacy-conscious professionals
• Journalists, lawyers, or auditors
• Anyone sharing or receiving documents from unknown sources

Demo

To test the service:

1. Send an email to [e-mail] with the subject: register
2. You’ll receive a one-time verification link. Click it to verify your email
3. Send another email to [e-mail] with a PDF attached
4. Wait about a minute and receive a sanitized version in your inbox

PDF size limit: 5 MB

Recommended page limit: 25 pages

Usage limit: Each verified user can sanitize up to 3 PDFs

Judges: If you need your usage limit increased for evaluation, please email [e-mail].

Code Repository

GitHub: https://github.com/rezelco/purifypdf-n8n

rezelco / purifypdf-n8n

Email-based PDF sanitizer using Postmark, PDF.co, Airtable, and n8n

PurifyPDF – Email-Based PDF Sanitizer

PurifyPDF is a privacy-first PDF sanitization workflow built using n8n, Postmark, PDF.co, and Airtable.

Users send a PDF as an email attachment to [e-mail], and the system returns a sanitized version, free of metadata, embedded scripts, and potentially unsafe content.

---

🚀 Demo

1. Send an email to [e-mail] with the subject: register
2. You’ll receive a verification link. Click to activate your email
3. Send another email with a PDF attached
4. Receive a sanitized version in your inbox

Limits

• Max PDF size: 5 MB
• Recommended page count: 25
• Each user may sanitize up to 3 files

---

🧰 Tech Stack

• n8n – Orchestrates workflow logic
• Postmark – Handles incoming and outgoing emails
• PDF.co – Converts and rebuilds PDFs for sanitization
• Airtable – Tracks users, limits, and verification

---

🔒 Privacy

PurifyPDF never stores files permanently. All PDFs are purged automatically after one hour. Only metadata…

View on GitHub

This repository includes:

• The full sanitized n8n workflow (purifypdf.json)
• MIT License and setup documentation

See the README for installation steps, required credentials, and detailed architecture.

How I Built It

PurifyPDF is built entirely in n8n, using no-code and low-code logic to orchestrate document processing, verification, and email flows.

The goal was to create something that feels invisible to users — no apps, no dashboards — just smart automation behind a simple email address.

Tech Stack

• n8n – Manages the full automation pipeline, including webhook ingestion, token generation, user tracking, and email sending.
• Postmark – Powers both inbound and outbound email. Incoming attachments are parsed through webhooks, and outgoing messages are branded, responsive, and fast.
• PDF.co – Sanitizes documents by converting each page to an image and rebuilding a new, clean PDF — free of metadata, scripts, and embedded content.
• Airtable – Stores user records, verification tokens, timestamps, and usage limits.
• JavaScript (Function nodes) – Used for logic branching, token generation, rate limiting, and retry logic inside the n8n flow.

Design Features

• Email-first UX – Every interaction happens through email. No UI required.
• One-click user registration – Email-based verification with expiring tokens
• Retry handling – Long-running PDF conversions use polling + wait loops
• Usage limits – Users can sanitize up to 3 PDFs unless upgraded
• Security & privacy – Files are stored temporarily and purged after processing

n8n Flow

Why I Chose Postmark

Postmark made it easy to:

• Receive emails and attachments via webhooks
• Monitor all incoming and outgoing email activity — incredibly helpful for debugging and delivery tracking
• Seamlessly integrate with n8n, making it easy to trigger flows, parse messages, and send responses without glue code

Challenge Reflection

This project started with a real, everyday problem at home. I found out my wife keeps a separate laptop that she uses only to open vendor invoices. After opening them, she prints the files, walks them to a second computer, and scans them back in — all to avoid the risk of opening untrusted PDFs on her main machine.

It was a clever workaround, but it got me thinking: in a world full of automation tools, why are we still physically printing documents just to feel safe?

That idea became the foundation for PurifyPDF. I wanted to build something simple, trustworthy, and accessible — a tool that requires no apps, no learning curve, and no new habits. If someone like my wife could use it without friction, that meant it could help a lot of other people too.

The Postmark Challenge was the perfect setting to bring it to life. Postmark made handling inbound and outbound email effortless, and pairing it with n8n and PDF.co gave me the flexibility to build a secure, responsive service without writing a backend from scratch.

This was one of the most rewarding projects I've worked on. It solves a real problem, feels invisible to the user, and showcases just how powerful email-driven automation can be.

License

MIT License

The name PurifyPDF and associated branding (e.g., logo, domain name) are not covered by the MIT license and may not be used without permission.