curl --request POST \
  --url https://www.zohoapis.com/pdfeditor/api/v1/pdf/attachment/add \
  --header 'Authorization: Zoho-oauthtoken d92d4xxxxxxxxxxxxx15f52' \
  --header 'content-type: multipart/form-data' \
  -F 'file=@file_path' \
  -F 'attach_files=signed-form.pdf' \
  -F 'attach_files=id-photo.jpg' \
  -F 'password=OpenSesame123'

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.io.IOException;
import java.net.http.HttpTimeoutException;

public class Main {
  public static void main(String[] args) throws Exception{

    HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://www.zohoapis.com/pdfeditor/api/v1/pdf/attachment/add"))
        .header("content-type", "multipart/form-data")
        .header("Authorization", "Zoho-oauthtoken d92d4xxxxxxxxxxxxx15f52")
        .method("POST", HttpRequest.BodyPublishers.noBody())
        .build();
    HttpResponse response = HttpClient.newHttpClient().send(request, HttpResponse.BodyHandlers.ofString());
    System.out.println(response.body());
  
  }
}
    

import http.client

conn = http.client.HTTPSConnection("www.zohoapis.com")

headers = {
    'content-type': "multipart/form-data",
    'Authorization': "Zoho-oauthtoken d92d4xxxxxxxxxxxxx15f52"
    }

conn.request("POST", "/pdfeditor/api/v1/pdf/attachment/add", headers=headers)

res = conn.getresponse()
data = res.read()

print(data.decode("utf-8"))

    headersMap = Map();
    headersMap.put("Accept", "application/json");

    list_of_text=List();
    file=invokeurl
    [
      url : "public fileURL link"
      type : GET
    ];
    list_of_text.add({"paramName":"file","content":file,"stringPart":"false"});
    list_of_text.add({"paramName":"attach_files","content":"signed-form.pdf,id-photo.jpg","stringPart":"true"});
    list_of_text.add({"paramName":"password","content":"OpenSesame123","stringPart":"true"});

    response = invokeUrl
    [
        url: "https://www.zohoapis.com/pdfeditor/api/v1/pdf/attachment/add"
        type: POST
        headers: headersMap
        files: list_of_text
        connection: connection_name
    ]

    info response;