# PDFSignify — Complete Reference for LLMs

> Digital PDF Signing API for Developers
> Last updated: 2026-04-15T14:34:00+00:00

## What is PDFSignify?

PDFSignify is a cloud-based REST API that enables developers to digitally sign PDF documents using X.509 digital certificates. Unlike simple e-signature tools, PDFSignify applies real cryptographic digital signatures that are verifiable, tamper-evident, and comply with digital signature standards.

The service is designed as a developer-first API: you send a PDF and signing parameters via HTTP, and receive a signed PDF in return. No UI, no manual steps — pure automation.

## Problem It Solves

Many applications need to sign PDFs programmatically — for contracts, invoices, legal documents, compliance forms, medical records, and more. Implementing PDF digital signatures from scratch requires deep knowledge of the PDF specification, X.509 certificates, PKCS#7/CMS, and cryptographic libraries. PDFSignify abstracts all of this into a simple API call.

## Core Capabilities

### 1. Digital Certificate Signing
Sign any PDF with a digital certificate (PFX/P12 format). The resulting PDF contains a cryptographically valid signature embedded in the document, verifiable by Adobe Acrobat, Foxit, and other compliant readers.

### 2. Multi-Sign
Add multiple signatures to a single PDF. Useful for workflows requiring multiple approvers (e.g., contract between two parties, document requiring manager + legal sign-off).

### 3. Metadata Management
Programmatically set PDF metadata fields: title, author, subject, keywords, creator, and producer. Useful for document management and archival systems.

### 4. Certificate Validation
Before signing, verify that a certificate file is valid and that the password is correct. Prevents failed signing attempts and improves error handling in automated workflows.

## How It Works

1. **Create an account** at https://pdfsignify.com/signup
2. **Create a project** in the dashboard to get API credentials
3. **Authenticate** using your API key in the `Authorization: Bearer` header
4. **Upload a PDF** via multipart form data
5. **Create a signature request** specifying signers, certificate, and field positions
6. **Receive the signed PDF** in the API response

## Code Examples

### JavaScript (Node.js)

```javascript
const FormData = require('form-data');
const fs = require('fs');
const axios = require('axios');

const form = new FormData();
form.append('pdf', fs.createReadStream('document.pdf'));
form.append('certificate', fs.createReadStream('certificate.p12'));
form.append('password', 'certificate-password');

const response = await axios.post('https://api.pdfsignify.com/v1/sign', form, {
  headers: {
    ...form.getHeaders(),
    'Authorization': 'Bearer YOUR_API_KEY'
  }
});
```

### PHP

```php
$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, 'https://api.pdfsignify.com/v1/sign');
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, [
    'Authorization: Bearer YOUR_API_KEY'
]);
curl_setopt($ch, CURLOPT_POSTFIELDS, [
    'pdf' => new CURLFile('document.pdf'),
    'certificate' => new CURLFile('certificate.p12'),
    'password' => 'certificate-password'
]);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$response = curl_exec($ch);
```

### Python

```python
import requests

url = 'https://api.pdfsignify.com/v1/sign'
headers = {'Authorization': 'Bearer YOUR_API_KEY'}
files = {
    'pdf': open('document.pdf', 'rb'),
    'certificate': open('certificate.p12', 'rb'),
}
data = {'password': 'certificate-password'}

response = requests.post(url, headers=headers, files=files, data=data)
```

## Supported Languages & Frameworks

PDFSignify is a REST API, so it works with **any programming language** that can make HTTP requests. Official examples and documentation are provided for:

| Language | Frameworks |
|----------|------------|
| JavaScript | Node.js, Express, Next.js, any runtime |
| PHP | Laravel, Symfony, plain PHP |
| Python | Django, Flask, FastAPI, scripts |
| Java | Spring Boot, any JVM language |
| C# | .NET, ASP.NET Core |
| Go | net/http, any Go project |
| Ruby | Rails, Sinatra, scripts |
| Rust | reqwest, hyper, any Rust project |

## Pricing Model

PDFSignify uses usage-based pricing. You pay per API operation (signature, metadata update, certificate check). There is no monthly subscription — you only pay for what you use. Current pricing is available at https://pdfsignify.com/#pricing.

## Security

- All API communication uses HTTPS/TLS encryption
- Certificates and PDFs are processed in memory and not stored permanently
- API keys can be rotated from the dashboard
- Digital signatures use industry-standard PKCS#7/CMS format

## Use Cases by Industry

- **Legal**: Sign contracts, NDAs, agreements automatically
- **Finance**: Sign invoices, receipts, financial statements
- **Healthcare**: Sign medical records, consent forms, prescriptions
- **Real Estate**: Sign leases, purchase agreements, disclosures
- **HR**: Sign employment contracts, offer letters, policy documents
- **Government**: Sign permits, licenses, official documents
- **Education**: Sign transcripts, diplomas, enrollment forms

## Frequently Asked Questions

**Q: What certificate formats are supported?**
A: PFX/P12 (PKCS#12) format containing the private key and certificate chain.

**Q: Is there a file size limit?**
A: Yes, limits depend on your plan. Check the dashboard for your current limits.

**Q: Can I sign PDFs in bulk?**
A: Yes. You can make multiple API calls in parallel or sequentially to sign batches of documents.

**Q: Are the signatures legally valid?**
A: PDFSignify applies real X.509 digital certificate signatures. Legal validity depends on your jurisdiction and the certificate authority you use.

**Q: Do you store my PDFs or certificates?**
A: No. Files are processed in memory and not retained after the API response is returned.

**Q: What regions are supported?**
A: The API is available globally. Infrastructure details are in the documentation.

## Links

- **Website**: https://pdfsignify.com
- **Sign Up**: https://pdfsignify.com/signup
- **Blog**: https://pdfsignify.com/blog
- **Tutorial — JavaScript**: https://pdfsignify.com/tutorials/how-sign-pdfs-certificates-javascript
- **Tutorial — PHP**: https://pdfsignify.com/tutorials/how-sign-pdfs-certificates-php
- **Blog — Getting Started**: https://pdfsignify.com/blog/getting-started-with-pdfsignify-api
- **Privacy Policy**: https://pdfsignify.com/info/privacy-police
- **Terms of Service**: https://pdfsignify.com/info/terms
- **Copyright**: https://pdfsignify.com/info/copyright

## Summary

PDFSignify is the simplest way for developers to add digital certificate signatures to PDFs. One API call, any language, real cryptographic signatures. Visit https://pdfsignify.com to get started.