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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.
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.
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.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.
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.
Combine PDFs instantly in your browser. No installation required.
$ pip install requests
File uploads must use multipart/form-data format. PDF API accepts a single file upload.
| Parameter | Required | Type | Default | Description |
|---|---|---|---|---|
| file | No | multipart/form-data | - | The PDF file to process. Only used if you're uploading a file instead of using file_id. |
All parameters must be included as query parameters. Any parameters sent in the form data will be ignored.
| Parameter | Required | Type | Default | Description |
|---|---|---|---|---|
| file_id | No | Array<String> | - | The unique ID of a file already present on our server. Use this instead of uploading the file again. |
| output | No | String | merged_output | Name of the output PDF (without extension). |
| destroy | No | Boolean | false | If true, we delete the input files immediately after generating the output. |
| Parameter | Required | Type | Default | Description |
|---|---|---|---|---|
| webhook_url | No | String | - | The URL where we'll send the webhook notification after the task completes. Authentication parameters in the URL (e.g., ?auth=token123) are passed as-is. |
| webhook_failure_notification | No | Boolean | false | If true, we'll send an email notification if the webhook request fails after 3 retries. The email goes to the requesting user or their org admin if user is part of an organization. |
| Header | Required | Type | Default | Description |
|---|---|---|---|---|
| X-Webhook-Authorization | No | String | - | Custom authorization header sent with the webhook request. Format: Key:Value (e.g., Authorization:Bearer token123). |
Explore detailed response fields including field names, data types, requirements, and descriptions in the interactive Response Table below. For complete response documentation click here.
Use these endpoints to manage files and check task status.
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.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.multipart/form-data request. Each file receives a unique file_id that can be used with the PDF APIs.file_id for uses with the PDF APIs.| HTTP Status | Reasons |
|---|---|
| 400 | Invalid PDF File: Please provide a valid PDF file. We don't support other types. |
| 400 | Missing File or ID: You must provide either a file or a file ID. |
| 400 | Invalid Parameter: The value for 'param_name' is invalid. |
| 404 | File ID Not Found: Please provide a valid file ID. |
| 500 | File Saving Exception: An unknown error occurred while saving. Try again later. |
| 500 | Internal Server Error: Internal Server Error Occurred. |
These errors might appear in the task-status response if the background job fails.
| Error | Description |
|---|---|
Invalid PDF File | The provided file is not a valid PDF file. |
File Saving Exception | An unknown error occurred while saving the file. Try again later. |
PDF Generation Exception | An unknown error occurred while generating the PDF. Try again later. |
Internal Server Error | Internal Server Error Occurred. |
Encrypted PDF Provided | The provided PDF file is encrypted. Please decrypt it first to perform operations. |
Follow these steps to merge PDF files using the API. The process involves uploading files, checking the task status, and downloading the result.
You can merge PDFs by uploading files directly (multipart upload) or referencing a file_id of stored files, or mixing both.
# 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" }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'
Notes:
destroy=true parameter to delete input files after merge completes (returns only taskId)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.
# Response (completed) { "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d", "status": "completed", "outputFileId": "9b2e7f3a-5c8d-4e1b-a6f9-0d3c8e7b2a5f", "outputFileName": "processed_document.pdf", "createdAt": "2025-01-26 10:30:00", "expiresAt": "2025-01-27 10:30:00" } # Response (failed) { "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d", "status": "failed", "error": "Invalid PDF File", "message": "The provided file is not a valid PDF file.", "createdAt": "2025-01-26 10:30:00" }curl -X GET "https://api.apifreaks.com/v1.0/pdf/task-status?taskId=04a06cd5-158d-4191-a45b-6f58249c599d" \ -H "X-apikey: YOUR_API_KEY"
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 "https://api.apifreaks.com/v1.0/pdf/download?fileId=9b2e7f3a-5c8d-4e1b-a6f9-0d3c8e7b2a5f" \ -H "X-apikey: YOUR_API_KEY" \ --output output.pdf
Get automatic notifications when your merge task completes instead of polling the task status endpoint. Good for event-driven applications and real-time document processing.
Add webhook_url to your merge request. We'll send a POST request to this URL when the task finishes (either completed or failed).
Example Request:
# Response { "taskId": "04a06cd5-158d-4191-a45b-6f58249c599d", "inputIds": [ "566dc743-d8fe-4943-8cef-61e5d3d6096c", "0d8371dc-734a-42b8-b941-64977fcf8183" ] }curl -X 'POST' \ 'https://api.apifreaks.com/v1.0/pdf/merge?output=merged_with_webhook&webhook_url=https://yourdomain.com/webhook/pdf-merge' \ -H 'X-apiKey: YOUR_API_KEY' \ -F 'file=@/path/to/document1.pdf' \ -F 'file=@/path/to/document2.pdf'
Webhook delivery will be attempted up to 3 times. If all retries fail and webhook_failure_notification is enabled, we'll send an email notification to the requesting user or their organization admin.
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
Example with custom authorization:
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'
When your task completes, we send a POST request to your webhook_url with these headers:
| Header | Description | Example |
|---|---|---|
Content-Type | Always application/json | application/json |
X-Signature | HMAC-SHA256 signature of the request body using your API key. Use this to verify the payload is authentic. | 4a7d1ed414474e4033ac29ccb8653d9b |
| Custom Header | (If provided) Your custom header from X-Webhook-Authorization | Authorization: Bearer token123 |
The webhook payload contains the same response structure as the Task Status API endpoint when checked for the task ID. For a comprehensive view of the webhook response structure and detailed field descriptions, explore the interactive Response Table.
Note: TheinputIds field is excluded from the webhook response when the destroy parameter is set to true in the original request.Use the X-Signature header to verify webhook requests actually came from API Freaks and weren't tampered with.
How the signature works:
X-Signature header valueTo verify the webhook:
X-Signature header valueImportant: Don't transform or process the raw request body before verification. Adding whitespace or other formatting creates a different signature and verification will fail.
To use the Merge PDF 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.
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.