Digital signatures API

Use this API to sign PDFs digitally with SOC 2-audited, certificate-based workflows. Sign, manage, and validate legally binding documents in your apps, websites, and platforms using a reliable cloud API.

Legally binding and cryptographically secure

Digitally sign PDF documents with digital certificates that support legal, regulatory, and compliance-oriented workflows such as eIDAS and related enterprise signing requirements.

Built for seamless integration

Use REST, Postman, JavaScript, Python, Java, C#, PHP, or HTTP to sign and validate PDF documents in your own platform without dealing with complex certificate workflows or signing infrastructure.

Try it instantly on Zapier

No code? No problem. Cryptographically sign new PDF files in Google Drive using our Zapier integration, and automatically save the signed copies back to Google Drive.


Try it out

This example will sign your document with a Nutrient certificate.


Try it out in three steps

  1. Add a PDF named document.pdf to your project folder.
  2. Run the code from the same folder.
  3. Open result.pdf to see the output.
curl -X POST https://api.nutrient.io/sign \
-H "Authorization: Bearer your_api_key_here" \
-o result.pdf \
--fail \
-F file=@document.pdf \
-F data='{
"signatureType": "cades",
"cadesLevel": "b-lt"
}'

Start now

Create an account to access your API key and start with 200 free credits

Start building with DWS Processor API in minutes — no payment information required.

Already have an account? Sign in →

How does it work?

Obtain the document to be signed

Create signing fields

Collect signer approval

For example, collect ink signatures from all users who need to approve the document before the final digital signature step.


Authenticate

Ensure the correct user is signing the document


Digitally sign

Use Nutrient’s digital seal (certificate), which guarantees that a document wasn’t tampered with after signing. Tampering with the document in any way invalidates the signature.


Most common next steps

Connect digital-signature evaluation to getting started, pricing, compliance, and the broader Processor platform

After validating digital-signature workflows, continue to PDF security if the workflow also needs password protection and permissions, getting started for API key setup, the Postman collection for the fastest first request, Processor API pricing for credits, or the Processor API overview for broader DWS evaluation of digital signature, certificate-based, compliance-ready PDF signing.


Security is our top priority

No document storage

No input or resulting documents are stored on our infrastructure. All files are deleted as soon as a request finishes. Alternatively, check out our self-hosted product.

HTTPS encryption

All communication between your application and Nutrient is done via HTTPS to ensure your data is encrypted when it’s sent to us.

Safe payment processing

All payments are handled by Paddle. Nutrient DWS Processor API never has direct access to any of your payment data.


Ready to try it?

Create an account to get your DWS Processor API key and start making API calls.