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APIs/Merge PDF API

Merge PDF API - Instantly Combine PDFs at Scale

Our PDF Merge API enables you to combine multiple PDF files into a single document through a simple REST endpoint. Whether you're merging two invoices or consolidating hundreds of report pages, our API handles it all while maintaining their original quality. Process any number of PDF files in a single request. The API preserves all fonts, images, formatting, and document structure without compression or quality loss. You can upload files directly, reference previously stored files by their File IDs, or use combination of both file uploads and file IDs in your workflows.

Built for production environments, we support asynchronous request processing and webhook notification support so you can easily integrate document merging into your automation systems and applications with minimal code, maximum reliability and zero data retention policy.

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Features

Asynchronous Processing

Upon successful request, our API immediately returns a 200 OK response with a unique Task ID, processing your file in the background. You can track the task progress via our Task Status API using the unique Task ID.

Webhook Notifications

If you don't want to poll for task status, you can simply provide the webhook data in your request. Instead of manually checking status, we will automatically notify your endpoint the moment the task processing is completed.

Zero Data Retention

Your privacy matters. When you set the destroy parameter, your files are permanently wiped from our servers immediately after processing finishes, ensuring complete data security. If destroy is not set, files are retained up to 30 days based on user's plan.

No Quality Loss

We keep your original document's quality. All things like fonts, pictures, and vector graphics, and the look do not change from original file. No compressing, downgrading, and you do not lose quality.

Large File Support

Merge large PDF files full of assets without worrying about limits on file numbers. Send as many files as you need in a single request up to a 1GB payload size limit.

Free Web Tool

Need to quickly Merge PDFs files in browser?

Combine multiple PDF files into one perfectly ordered document.

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API Endpoint

POSThttps://api.apifreaks.com/v1.0/pdf/merge

Test

Explore the complete API reference with detailed request parameters, response fields, error codes, and code examples visit API Reference.

LANGUAGE


$ pip install requests
import requests

url = "https://api.apifreaks.com/v1.0/pdf/merge?file_id=ba3fc487-4df6-4aea-9a72-aa8d4ecec25d&destroy=true&output=merged_pdf.pdf"

payload = {}
files=[
  ('file',('file.pdf',open('/path/to/file.pdf','rb'),'application/pdf'))
]
headers = {
  'X-apiKey': 'API-KEY'
}

response = requests.request("POST", url, headers=headers, data=payload, files=files)

print(response.text)

Utility & Resource APIs

Use these endpoints to manage files and check task status.

Task Status API

Check real-time status and retrieve input/output file ID(s) using the unique task_id. The response includes creation and expiry timestamps to help you track result availability, along with specific error details if a task fails. Results are retained for up to 7 days, depending on the operation.

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File Status API

Retrieve detailed metadata for any file using its unique file_id. Returns details including file name, size, type, and creation/deletion timestamps. Generated or uploaded files are retained up to 30 days based on user's plan, unless destroy is enabled to delete them immediately. You can use this endpoint to check if the file has expired using its file_id.

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File Download API

Download any file from API Freaks server using its file ID. Works for both processed PDF files and ZIP archives containing multiple output files.

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PDF Delete API

Permanently delete a specific file you uploaded or generated using the file ID which you no longer need.

Try PDF Delete API

Files List API

Retrieve a list of all your PDF files stored on API Freaks server, with their file names and corresponding file IDs. Organization admins and maintainers can view all files in their organization, while members see only their own.

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File Upload API

Upload one or multiple PDF files in a single multipart/form-data request. Each file receives a unique file_id that can be used with the PDF APIs.

Try File Upload API

Upload Binary API

Upload a single large as a raw binary stream. This method eliminates multipart boundary overhead, offering faster upload speeds for larger files. Returns a unique file_id for uses with the PDF APIs.

Try Upload Binary API

How-To-Guides

Merging PDFs

Follow these steps to merge PDF files using the API. The process involves uploading files, checking the task status, and downloading the result.

Step 1: Upload and Merge PDFs

You can merge PDFs by uploading files directly (multipart upload) or referencing a file_id of stored files, or mixing both.

curl -X POST "https://api.apifreaks.com/v1.0/pdf/merge?file_id=566dc743-d8fe-4943-8cef-61e5d3d6096c&file_id=0d8371dc-734a-42b8-b941-64977fcf8183&output=merged_document" \
  -H "X-apikey : YOUR_API_KEY" \
  -F "file=@/path/to/document1.pdf" \
  -F "file=@/path/to/document2.pdf"

# Standard Response

{
    "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d",
    "inputIds": [
        "7a9e4b12-f3c8-4d56-b7e1-8c2f9d0a3e6f",
        "3f8d5c21-a4b7-4e69-9c1d-2e7f8a0b5c9d",
        "566dc743-d8fe-4943-8cef-61e5d3d6096c",
        "0d8371dc-734a-42b8-b941-64977fcf8183"
    ]
}

# Response with destroy=true (No File Ids as they are deleted right away)
{
    "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d"
}

Notes:

You can upload any number of PDF files (up to 1GB total payload size)
Whether merging two files or a hundred, the Upload Binary API offers the most efficient way to upload large assets before processing.
All multipart files are processed first in the order they appear, then file IDs in their order
In the response above, the first two IDs are from the uploaded files, the last two are the file IDs you provided
Use the destroy=true parameter to delete input files after merge completes (returns only taskId)
File IDs must reference valid, active files stored on the API Freaks server. You can verify if a file is still available using the File Status API

Step 2: Check Task Status

After submitting a merge task, check its progress using the Task Status API with your taskId. The task goes through these statuses: queued, processing, completed, and failed.

curl -X GET "https://api.apifreaks.com/v1.0/pdf/task-status?task_id=04a06cd5-158d-4191-a45b-6f58249c599d" \
  -H "X-apikey: YOUR_API_KEY"

# Response (completed)
{
  "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d",
  "status": "completed",
  "createdAt": "2025-01-26 10:30:00",
  "outputUrls": [
    "https://api.apifreaks.com/v1.0/pdf/resource/download?resource_id=9b2e7f3a-5c8d-4e1b-a6f9-0d3c8e7b2a5f"
  ],
  "outputFileId": [
    "9b2e7f3a-5c8d-4e1b-a6f9-0d3c8e7b2a5f"
  ],
  "inputIds": [
    "7a9e4b12-f3c8-4d56-b7e1-8c2f9d0a3e6f",
    "3f8d5c21-a4b7-4e69-9c1d-2e7f8a0b5c9d",
    "566dc743-d8fe-4943-8cef-61e5d3d6096c",
    "0d8371dc-734a-42b8-b941-64977fcf8183"
  ],
  "expiresAt": "2025-01-27 10:30:00"
}

curl -X GET "https://api.apifreaks.com/v1.0/pdf/task-status?task_id=04a06cd5-158d-4191-a45b-6f58249c599d" \
  -H "X-apikey: YOUR_API_KEY"

# Response (failed)
{
  "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d",
  "status": "failed",
  "createdAt": "2025-01-26 10:30:00",
  "inputIds": [
    "7a9e4b12-f3c8-4d56-b7e1-8c2f9d0a3e6f",
    "3f8d5c21-a4b7-4e69-9c1d-2e7f8a0b5c9d",
    "566dc743-d8fe-4943-8cef-61e5d3d6096c",
    "0d8371dc-734a-42b8-b941-64977fcf8183"
  ],
  "error": "Invalid PDF File",
  "message": "The provided file is not a valid PDF file.",
  "expiresAt": "2025-01-27 10:30:00"
}

Step 3: Download Merged PDF

Once the task status shows “completed”, download your merged PDF using the File Download API with the outputFileId from the task status response.

curl -X GET "true?resource_id=9b2e7f3a-5c8d-4e1b-a6f9-0d3c8e7b2a5f" \
  -H "X-apikey: YOUR_API_KEY" \
  --output merged_document.pdf

Webhook Support

Get automatic notifications when your task completes instead of polling the task status endpoint. Good for event-driven applications and real-time document processing.

Add webhook_urlto your request. We'll send a POST request to this URL when the task finishes (either completed or failed).

See the Complete Webhook Example section below for a full demonstration including custom authorization headers.

Webhook Delivery

Webhook delivery will be attempted up to 3 times. If all retries fail and webhook_failure_notificationis enabled, we'll send an email notification to the requesting user or their organization admin.

Custom Authorization Header

Use X-Webhook-Authorization to add a custom header to webhook requests for endpoint security.

Format: Key:Value

Example: If you send Authorization:Bearer token123, the webhook request will include: Authorization: Bearer token123

See the Complete Webhook Example below for a full demonstration.

Complete Webhook Example

Here's a complete example showing webhook integration with custom authorization header and failure notifications:

curl -X 'POST' \
  'https://api.apifreaks.com/v1.0/pdf/merge?webhook_url=https://yourdomain.com/webhook/pdf-merge&webhook_failure_notification=true' \
  -H 'X-apiKey: YOUR_API_KEY' \
  -H 'X-Webhook-Authorization: Authorization:Bearer token123' \
  -F 'file=@/path/to/document.pdf'

# Response
{
  "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d",
  "inputIds": [
    "566dc743-d8fe-4943-8cef-61e5d3d6096c"
  ]
}

Webhook Request Format

When your task completes, we send a POST request to your webhook_url with these headers:

Header	Description
`Content-Type`	Always `application/json`
`X-Signature`	HMAC-SHA256 signature of the request body using your API key. Use this to verify the payload is authentic.
Custom Header	(If provided) Your custom header from `X-Webhook-Authorization`

Webhook Response

The webhook payload contains the same response structure as the Task Status API endpoint when checked for the task ID.

Note: The inputIds field is excluded from the webhook response when the destroy parameter is set to true in the original request.

Verifying Webhook Authenticity

Use the X-Signatureheader to verify webhook requests actually came from API Freaks and weren't tampered with.

How the signature works:

We compute an HMAC-SHA256 hash of the request body using your API key as the secret
We Base64-encode the result
We send this as the X-Signature header value

To verify the webhook:

Take the raw payload body (JSON string exactly as received without parsing it)
Compute HMAC-SHA256 of the payload using your API key as the secret
Base64-encode the result of the hash
Compare with the X-Signature header value

Important:Don't transform or process the raw request body before verification. Adding whitespace or other formatting creates a different signature and verification will fail.

Pricing

To use this API, API credits are required. Charges apply only for successful queries, defined by a 2xx status code. If a request results in a 4xx or 5xx status code, no credits will be deducted, and any credits already charged will be refunded. In the event of a Task Processing Error, a maximum of 200 credits will be refunded. Surcharges for additional file sizes are non-refundable.

For each successful request, 200 credits will be charged. 1 extra credit will be charged per MB beyond 50 MB.

Utilize the Credits Usage API to efficiently monitor your recent consumption of both one-off and subscription credits. This API provides a streamlined way to track and manage your credit usage, ensuring you stay informed about your remaining balance and can optimize your resource allocation effectively.

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