B2B digital signature platform

One API for PDF, Fiscal XML and Digital Diploma signing.

A single integration for medical, fiscal, educational and generic PDF workflows. Support for cloud, local A3 and A1 certificates with full traceability.

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Connector JS

const connector = createSignerConnector({
  apiBaseUrl: 'https://4signer.com/api',
  bearerToken: 'YOUR_TOKEN'
});

const result = await connector.sign({
  documentId: 'contract-001',
  documentType: 'pdf',
  certificateMode: 'cloud',
  documentFile: pdfBlob, // File ou Blob
  providerHint: 'birdid',
  requestOptions: {
    metadata: {
      reason: 'Contract signature',
      location: 'São Paulo, BR',
      name: 'Signer name',
      contact: 'email@example.com'
    }
  }
});

// Signed document
const download = await connector.getDownloadUrl({
  signatureId: result.signature_id
});

const connector = createSignerConnector({
  apiBaseUrl: 'https://4signer.com/api',
  bearerToken: 'YOUR_TOKEN'
});

const result = await connector.sign({
  documentId: 'nfe-001',
  documentType: 'xml',
  certificateMode: 'cloud',
  documentFile: xmlFile, // File XML
  providerHint: 'serproid',
  xmlProfile: 'fiscal',
  xmlPolicy: 'nfe-4.00',
  xmlPolicyParameters: {
    signed_element_local_name: 'infNFe', // XML tag to sign
    id_attribute: 'Id'
  }
});

const download = await connector.getDownloadUrl({
  signatureId: result.signature_id
});

Products by scenario

Choose the best flow for your product: general PDF, medical documents, fiscal XML or digital diploma.

PDF

PDF documents

Contracts, HR, legal and operations with digital signing in the same flow.

PDF

Medical documents

Sign prescriptions, exams and medical certificates in a direct workflow with legal validity.

Tax documents

NFe, CTe and NFSe

Fiscal XML signing.

Digital diploma

XAdES and ICP-Brasil

Specialized flow for academic XML signing with advanced per-tag policies.

How it works in 3 steps

1. Integrate

Connect API or Connector JS

Use one auth and payload pattern for every document type.

2. Sign

Choose mode per request

A1, local A3 or cloud with the right flow for PDF, fiscal XML or diploma.

3. Receive

Download + webhook status

Track signatures, auditing and events in real time in your system.

PDF flow Medical flow Fiscal XML flow Diploma flow

Why choose 4signer?

Fewer integrations, lower operational cost, and legally valid documents in one place.

One API for everything

Cloud, A3 (token or smart card), and A1 in the same endpoint. Choose the mode by document or by user without switching vendors.

Legal validity

Signatures with ICP-Brasil certificate and timestamp. Documents ready for audit and compliance.

Dashboard and traceability

Dashboard with signature history, account/token logs, webhooks, and automatic retry. Full visibility for your team.

Built for your business

Management software that must sign contracts, prescriptions, reports, or documents with digital certificates.

Clinics and medical records ERPs and management systems Fintechs and contracts Labs and reports Law firms and legal documents

Cloud certificate signing

The API opens the session, the signer approves in the provider app (e.g., BirdID, Certisign, Serpro ID), and the final signed document returns to your system.

The signer approves on mobile, without a physical token.
Ideal for prescriptions, medical certificates, and remote documents.
Support for multiple providers in a single integration.

Client system

4signer API

Provider Cloud

DOC

curl -X POST "https://4signer.com/api/v1/connector/v1/sessions" \\
  -H "Authorization: Bearer TOKEN_DA_ACCOUNT" \\
  -H "Content-Type: application/json" \\
  -d '{
    "document_id": "contract-1001",
    "document_type": "pdf",
    "certificate_mode": "cloud",
    "provider_hint": "birdid",
    "document_content_base64": "JVBERi0x...",
    "metadata": {
      "reason": "Commercial contract"
    },
    "request_options": {
      "timestamp": {
        "enabled": true,
        "url": "https://tsa.example.com/rfc3161",
        "token": "TSA_TOKEN"
      }
    }
  }'

curl -X POST "https://4signer.com/api/v1/connector/v1/sessions" \\
  -H "Authorization: Bearer TOKEN_DA_ACCOUNT" \\
  -H "Content-Type: application/json" \\
  -d '{
    "document_id": "nfe-1001",
    "document_type": "xml",
    "certificate_mode": "cloud",
    "provider_hint": "serproid",
    "signature_profile": "fiscal",
    "signature_policy": "nfe-4.00",
    "signature_policy_parameters": {
      "signed_element_local_name": "infNFe",
      "id_attribute": "Id"
    },
    "request_options": {
      "timestamp": {
        "enabled": true,
        "url": "https://tsa.example.com/rfc3161",
        "token": "TSA_TOKEN"
      }
    },
    "document_content_base64": "PD94bWwgdmVyc2lvbj0iMS4wIi4uLg=="
  }'

Local signing with Desktop Agent (A3 token/smart card)

The frontend requests a local session, the agent installed on the signer's computer signs with token or smart card, and sends the result back to the API.

Uses the existing professional A3 certificate (token/card).
Local signing at the workstation, without depending on cloud apps.
Ephemeral token and configurable TTL for stronger security.

Frontend

Agent 127.0.0.1

4signer Backend

DOC

OK

Connector JS

const connector = createSignerConnector({
  apiBaseUrl: 'https://4signer.com/api',
  bearerToken: 'YOUR_TOKEN'
});

const result = await connector.sign({
  documentId: 'doc-001',
  certificateMode: 'local',
  documentFile: pdfBlob,
  requestOptions: {
    timestamp: {
      enabled: true,
      url: 'https://tsa.example.com/rfc3161',
      token: 'TSA_TOKEN'
    }
  }
});

const download = await connector.getDownloadUrl({
  signatureId: result.signature_id
});

const connector = createSignerConnector({
  apiBaseUrl: 'https://4signer.com/api',
  bearerToken: 'YOUR_TOKEN'
});

const result = await connector.sign({
  documentId: 'diploma-001',
  documentType: 'xml',
  certificateMode: 'local',
  documentFile: diplomaXmlFile,
  xmlProfile: 'xml-xades-diploma',
  xmlPolicy: 'diploma-icpbrasil-xades-1.0',
  xmlPolicyParameters: {
    signed_element_local_name: 'DadosDiploma', // XML tag to sign
    id_attribute: 'id'
  },
  requestOptions: {
    timestamp: {
      enabled: true,
      url: 'https://tsa.example.com/rfc3161',
      token: 'TSA_TOKEN'
    }
  }
});

const download = await connector.getDownloadUrl({
  signatureId: result.signature_id
});

A1: PFX file or stored credential (PDF and XML)

Batch or automated PDF/XML signing with A1 certificate: send PFX in the request or store once and reuse.

A1 file: ideal for occasional flows or migration.
Stored A1: less traffic and lower latency at high volume.
Synchronous or asynchronous processing as needed.

A1 File

Sends PFX + password in the request.

Stored A1

Reuses stored certificate.

curl -X POST "https://4signer.com/api/v1/signatures/pdf" \\
  -H "Authorization: Bearer TOKEN_DA_ACCOUNT" \\
  -F "signature_method=local_pfx" \\
  -F "processing_mode=sync" \\
  -F "pdf=@/tmp/documento.pdf" \\
  -F "pfx=@/tmp/certificado.pfx" \\
  -F "pfx_password=SENHA" \\
  -F "request_options[timestamp][enabled]=1" \\
  -F "request_options[timestamp][url]=https://tsa.example.com/rfc3161" \\
  -F "request_options[timestamp][username]=tsa_user" \\
  -F "request_options[timestamp][password]=tsa_pass"

curl -X POST "https://4signer.com/api/v1/signatures/xml" \\
  -H "Authorization: Bearer TOKEN_DA_ACCOUNT" \\
  -F "signature_method=local_pfx" \\
  -F "processing_mode=sync" \\
  -F "xml=@/tmp/nfe.xml" \\
  -F "pfx=@/tmp/certificado.pfx" \\
  -F "pfx_password=SENHA" \\
  -F "request_options[timestamp][enabled]=1" \\
  -F "request_options[timestamp][url]=https://tsa.example.com/rfc3161" \\
  -F "request_options[timestamp][token]=TSA_TOKEN"

Webhook + operational monitoring

Your system is notified when signing succeeds or fails. Request/response logs and automatic retry reduce manual support.

Event signature.status_changed with status_to (signed, failed, etc.).
Up to 3 automatic retries; manual reprocessing in dashboard.
Full traceability for auditing and SLA.

Automatic retries

Up to 3 attempts, with manual reprocessing in the dashboard.

Register webhook

curl -X POST "https://4signer.com/api/v1/webhooks" \
  -H "Authorization: Bearer TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"url":"https://seu-site.com/webhook","max_attempts":3}'

Payload we send to your URL (POST JSON)

{
  "event": "signature.status_changed",
  "occurred_at": "2025-02-16T14:30:00.000000Z",
  "account": { "id": 1 },
  "signature": {
    "id": 42,
    "provider": "birdid",
    "processing_mode": "async",
    "status_from": "processing",
    "status_to": "signed",
    "external_id": "doc-1001",
    "error_code": null,
    "error_message": null,
    "started_at": "2025-02-16T14:29:58.000000Z",
    "completed_at": "2025-02-16T14:30:00.000000Z",
    "duration_ms": 2000
  }
}

One API

Cloud, A3 and A1

All signing modes in a single integrator.

Compliance and auditing

ICP-Brasil + carimbo do tempo

Legally valid documents, per-signature logs, and webhooks for your audit workflow.

Technical support

Docs + support

Complete documentation and deployment support.

Ready to sign PDF and XML with legal validity?

Subscribe and get rate limits, per-account logs, and a production operations dashboard.

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Supported certificates

Certificate models for each flow

Use the same backend for cloud operation, local file signing, and machine-installed certificates.

Cloud

BirdID, VIDaaS, SerproID and Certisign.

A1 digital file

PFX/P12 upload per request with secure password handling.

Installed Token or SmartCard

Local A3 via Desktop Agent integrated with Connector JS.