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.
Digitally sign PDF documents with digital certificates that support legal, regulatory, and compliance-oriented workflows such as eIDAS and related enterprise signing requirements.
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.
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.
This example will sign your document with a Nutrient certificate.
Try it out in three steps
document.pdf to your project folder.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" }'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\"}"package com.example.pspdfkit;
import java.io.File;import java.io.IOException;import java.nio.file.FileSystems;import java.nio.file.Files;import java.nio.file.StandardCopyOption;
import org.json.JSONObject;
import okhttp3.MediaType;import okhttp3.MultipartBody;import okhttp3.OkHttpClient;import okhttp3.Request;import okhttp3.RequestBody;import okhttp3.Response;
public final class PspdfkitApiExample { public static void main(final String[] args) throws IOException { final RequestBody body = new MultipartBody.Builder() .setType(MultipartBody.FORM) .addFormDataPart( "file", "document.pdf", RequestBody.create( MediaType.parse("application/pdf"), new File("document.pdf") ) ) .addFormDataPart( "data", new JSONObject() .put("signatureType", "cades") .put("cadesLevel", "b-lt").toString() ) .build();
final Request request = new Request.Builder() .url("https://api.nutrient.io/sign") .method("POST", body) .addHeader("Authorization", "Bearer your_api_key_here") .build();
final OkHttpClient client = new OkHttpClient() .newBuilder() .build();
final Response response = client.newCall(request).execute();
if (response.isSuccessful()) { Files.copy( response.body().byteStream(), FileSystems.getDefault().getPath("result.pdf"), StandardCopyOption.REPLACE_EXISTING ); } else { // Handle the error throw new IOException(response.body().string()); } }}using System;using System.IO;using System.Net;using RestSharp;
namespace PspdfkitApiDemo{ class Program { static void Main(string[] args) { var client = new RestClient("https://api.nutrient.io/sign");
var request = new RestRequest(Method.POST) .AddHeader("Authorization", "Bearer your_api_key_here") .AddFile("file", "document.pdf") .AddParameter("data", new JsonObject { ["signatureType"] = "cades", ["cadesLevel"] = "b-lt" }.ToString());
request.AdvancedResponseWriter = (responseStream, response) => { if (response.StatusCode == HttpStatusCode.OK) { using (responseStream) { using var outputFileWriter = File.OpenWrite("result.pdf"); responseStream.CopyTo(outputFileWriter); } } else { var responseStreamReader = new StreamReader(responseStream); Console.Write(responseStreamReader.ReadToEnd()); } };
client.Execute(request); } }}// This code requires Node.js. Do not run this code directly in a web browser.
const axios = require('axios')const FormData = require('form-data')const fs = require('fs')
const formData = new FormData()formData.append('data', JSON.stringify({ signatureType: "cades", cadesLevel: "b-lt"}))formData.append('file', fs.createReadStream('document.pdf'))
;(async () => { try { const response = await axios.post('https://api.nutrient.io/sign', formData, { headers: formData.getHeaders({ 'Authorization': 'Bearer your_api_key_here' }), responseType: "stream" })
response.data.pipe(fs.createWriteStream("result.pdf")) } catch (e) { const errorString = await streamToString(e.response.data) console.log(errorString) }})()
function streamToString(stream) { const chunks = [] return new Promise((resolve, reject) => { stream.on("data", (chunk) => chunks.push(Buffer.from(chunk))) stream.on("error", (err) => reject(err)) stream.on("end", () => resolve(Buffer.concat(chunks).toString("utf8"))) })}import requestsimport json
response = requests.request( 'POST', 'https://api.nutrient.io/sign', headers = { 'Authorization': 'Bearer your_api_key_here' }, files = { 'file': open('document.pdf', 'rb') }, data = { 'data': json.dumps({ 'signatureType': 'cades', 'cadesLevel': 'b-lt' }) }, stream = True)
if response.ok: with open('result.pdf', 'wb') as fd: for chunk in response.iter_content(chunk_size=8096): fd.write(chunk)else: print(response.text) exit()<?php
$FileHandle = fopen('result.pdf', 'w+');
$curl = curl_init();
curl_setopt_array($curl, array( CURLOPT_URL => 'https://api.nutrient.io/sign', CURLOPT_CUSTOMREQUEST => 'POST', CURLOPT_RETURNTRANSFER => true, CURLOPT_ENCODING => '', CURLOPT_POSTFIELDS => array( 'data' => '{ "signatureType": "cades", "cadesLevel": "b-lt" }', 'file' => new CURLFILE('document.pdf') ), CURLOPT_HTTPHEADER => array( 'Authorization: Bearer your_api_key_here' ), CURLOPT_FILE => $FileHandle,));
$response = curl_exec($curl);
curl_close($curl);
fclose($FileHandle);POST https://api.nutrient.io/sign HTTP/1.1Content-Type: multipart/form-data; boundary=--customboundaryAuthorization: Bearer your_api_key_here
--customboundaryContent-Disposition: form-data; name="data"Content-Type: application/json
{ "signatureType": "cades", "cadesLevel": "b-lt"}--customboundaryContent-Disposition: form-data; name="file"; filename="document.pdf"Content-Type: application/pdf
(file data)--customboundary--For example, collect ink signatures from all users who need to approve the document before the final digital signature step.
Ensure the correct user is signing the document
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
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.
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.
All communication between your application and Nutrient is done via HTTPS to ensure your data is encrypted when it’s sent to us.
All payments are handled by Paddle. Nutrient DWS Processor API never has direct access to any of your payment data.
Create an account to get your DWS Processor API key and start making API calls.