curl -X POST https://api.nutrient.io/build ^
  -H "Authorization: Bearer your_api_key_here" ^
  -o result.pdf ^
  --fail ^
  -F page1.png=@/path/to/page1.png ^
  -F page2.png=@/path/to/page2.png ^
  -F page3.png=@/path/to/page3.png ^
  -F page4.png=@/path/to/page4.png ^
  -F instructions="{\"parts\": [{\"file\": \"page1.png\"}, {\"file\": \"page2.png\"}, {\"file\": \"page3.png\"}, {\"file\": \"page4.png\"}]}"

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.JSONArray;
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(
        "page1.png",
        "/path/to/page1.png",
        RequestBody.create(
          MediaType.parse("image/png"),
          new File("/path/to/page1.png")
        )
      )
      .addFormDataPart(
        "page2.png",
        "/path/to/page2.png",
        RequestBody.create(
          MediaType.parse("image/png"),
          new File("/path/to/page2.png")
        )
      )
      .addFormDataPart(
        "page3.png",
        "/path/to/page3.png",
        RequestBody.create(
          MediaType.parse("image/png"),
          new File("/path/to/page3.png")
        )
      )
      .addFormDataPart(
        "page4.png",
        "/path/to/page4.png",
        RequestBody.create(
          MediaType.parse("image/png"),
          new File("/path/to/page4.png")
        )
      )
      .addFormDataPart(
        "instructions",
        new JSONObject()
          .put("parts", new JSONArray()
            .put(new JSONObject()
              .put("file", "page1.png")
            )
            .put(new JSONObject()
              .put("file", "page2.png")
            )
            .put(new JSONObject()
              .put("file", "page3.png")
            )
            .put(new JSONObject()
              .put("file", "page4.png")
            )
          ).toString()
      )
      .build();

    final Request request = new Request.Builder()
      .url("https://api.nutrient.io/build")
      .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/build");

      var request = new RestRequest(Method.POST)
        .AddHeader("Authorization", "Bearer your_api_key_here")
        .AddFile("page1.png", "/path/to/page1.png")
        .AddFile("page2.png", "/path/to/page2.png")
        .AddFile("page3.png", "/path/to/page3.png")
        .AddFile("page4.png", "/path/to/page4.png")
        .AddParameter("instructions", new JsonObject
        {
          ["parts"] = new JsonArray
          {
            new JsonObject
            {
              ["file"] = "page1.png"
            },
            new JsonObject
            {
              ["file"] = "page2.png"
            },
            new JsonObject
            {
              ["file"] = "page3.png"
            },
            new JsonObject
            {
              ["file"] = "page4.png"
            }
          }
        }.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('instructions', JSON.stringify({
  parts: [
    {
      file: "page1.png"
    },
    {
      file: "page2.png"
    },
    {
      file: "page3.png"
    },
    {
      file: "page4.png"
    }
  ]
}))
formData.append('page1.png', fs.createReadStream('/path/to/page1.png'))
formData.append('page2.png', fs.createReadStream('/path/to/page2.png'))
formData.append('page3.png', fs.createReadStream('/path/to/page3.png'))
formData.append('page4.png', fs.createReadStream('/path/to/page4.png'))

;(async () => {
  try {
    const response = await axios.post('https://api.nutrient.io/build', 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 requests
import json

response = requests.request(
  'POST',
  'https://api.nutrient.io/build',
  headers = {
    'Authorization': 'Bearer your_api_key_here'
  },
  files = {
    'page1.png': open('/path/to/page1.png', 'rb'),
    'page2.png': open('/path/to/page2.png', 'rb'),
    'page3.png': open('/path/to/page3.png', 'rb'),
    'page4.png': open('/path/to/page4.png', 'rb')
  },
  data = {
    'instructions': json.dumps({
      'parts': [
        {
          'file': 'page1.png'
        },
        {
          'file': 'page2.png'
        },
        {
          'file': 'page3.png'
        },
        {
          'file': 'page4.png'
        }
      ]
    })
  },
  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/build',
  CURLOPT_CUSTOMREQUEST => 'POST',
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => '',
  CURLOPT_POSTFIELDS => array(
    'instructions' => '{
      "parts": [
        {
          "file": "page1.png"
        },
        {
          "file": "page2.png"
        },
        {
          "file": "page3.png"
        },
        {
          "file": "page4.png"
        }
      ]
    }',
    'page1.png' => new CURLFILE('/path/to/page1.png'),
    'page2.png' => new CURLFILE('/path/to/page2.png'),
    'page3.png' => new CURLFILE('/path/to/page3.png'),
    'page4.png' => new CURLFILE('/path/to/page4.png')
  ),
  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/build HTTP/1.1
Content-Type: multipart/form-data; boundary=--customboundary
Authorization: Bearer your_api_key_here

--customboundary
Content-Disposition: form-data; name="instructions"
Content-Type: application/json

{
  "parts": [
    {
      "file": "page1.png"
    },
    {
      "file": "page2.png"
    },
    {
      "file": "page3.png"
    },
    {
      "file": "page4.png"
    }
  ]
}
--customboundary
Content-Disposition: form-data; name="page1.png"; filename="/path/to/page1.png"
Content-Type: image/png

(page1.png data)
--customboundary
Content-Disposition: form-data; name="page2.png"; filename="/path/to/page2.png"
Content-Type: image/png

(page2.png data)
--customboundary
Content-Disposition: form-data; name="page3.png"; filename="/path/to/page3.png"
Content-Type: image/png

(page3.png data)
--customboundary
Content-Disposition: form-data; name="page4.png"; filename="/path/to/page4.png"
Content-Type: image/png

(page4.png data)
--customboundary--