PDF Signing Privacy: Why Where You Sign Matters

Your PDF Contains More Than You Think

When you sign a PDF, you're often handling documents that contain sensitive personal information:

Contracts with your legal name, address, and payment terms
Tax forms with your social security number or tax ID
Employment agreements with salary and benefit details
Medical forms with health information
Lease agreements with your financial history
NDAs with proprietary business information

When you upload these documents to an online PDF tool, you're trusting that service with all of this data.

Server-Side vs Browser-Side Processing

There are two fundamentally different ways online PDF tools work:

Server-Side Processing (Most Tools)

Tools like Smallpdf, iLovePDF, DocuSign, and Adobe Acrobat Online upload your PDF to their servers for processing. This means:

Your document travels over the internet to their data center
It exists on their servers during processing (and sometimes after)
Their employees could theoretically access your files
The data is subject to the privacy laws of wherever their servers are located
If their servers are breached, your documents could be exposed

Most reputable services delete files after processing (Smallpdf says 1 hour, Sejda says 2 hours). But during that window, your sensitive documents exist on someone else's computer.

Browser-Side Processing (SigPDF)

SigPDF processes your PDF entirely within your web browser using client-side JavaScript. This means:

Your document never leaves your device
No data is transmitted over the internet
No server ever sees your file
There is nothing to delete because nothing was uploaded
Even if our website were hacked, your documents would be safe because they were never on our servers

This isn't just a marketing claim — it's a fundamental architectural difference. The PDF rendering, signature placement, and final PDF generation all happen in your browser using JavaScript libraries (pdf-lib and pdf.js).

How to Verify a Tool Processes Locally

Don't take any tool's word for it. Here's how to verify:

Open browser developer tools (F12 or Cmd+Option+I)
Go to the Network tab
Upload a PDF and sign it
Watch the network requests

With a truly browser-based tool, you should see no large file uploads to any server. With server-based tools, you'll see your PDF being sent to their API.

Why This Matters More Than You Think

Data Breach Risk

In 2025 alone, major data breaches exposed billions of records. PDF signing services store millions of documents. A single breach could expose contracts, tax forms, and personal information for thousands of users.

GDPR and Data Protection

Under the EU's GDPR, uploading a PDF containing personal data to a third-party server creates a data processing relationship. The service becomes a data processor, and you should technically verify their GDPR compliance, check their data processing agreement, and confirm where their servers are located.

With browser-based processing, none of this applies — no personal data is processed by any third party.

Corporate Compliance

Many companies have policies restricting where employee data and confidential documents can be stored. Using a server-based PDF signing tool may violate your company's data handling policies. Browser-based tools avoid this issue entirely.

What About Digital Signatures with Certificates?

Cryptographic digital signatures (as opposed to simple electronic signatures) require a Certificate Authority and typically do involve server communication. If you need a certified digital signature for regulatory compliance, you'll need a specialized tool that handles certificates.

For the vast majority of document signing — contracts, agreements, forms — a simple electronic signature is legally sufficient and can be done entirely in your browser.

The Bottom Line

When choosing a PDF signing tool, consider what's in the documents you're signing. For sensitive documents, a tool that processes everything in your browser provides fundamentally better privacy than one that uploads your files to a server.

Sign PDFs Privately with SigPDF →