# Merge PDF API (`api-center/merge-pdf-api`) Actor

Merge multiple PDFs from public URLs or file uploads into a single PDF and save the result to the run's key-value store.

- **URL**: https://apify.com/api-center/merge-pdf-api.md
- **Developed by:** [Leo Yan](https://apify.com/api-center) (community)
- **Stats:** 2 total users, 1 monthly users, 100.0% runs succeeded, 0 bookmarks
- **User rating**: No ratings yet

## Pricing

from $0.002 / actor start

This Actor is paid per event. You are not charged for the Apify platform usage, but only a fixed price for specific events.

Learn more: https://docs.apify.com/actors/running/actors-in-store.md#pay-per-event

## What's an Apify Actor?

An Actor is a serverless cloud program that runs on the Apify platform. It has two run modes.
In Batch mode, an Actor accepts a well-defined JSON input, performs an action which can take anything from a few seconds to a few hours,
and optionally produces a well-defined JSON output, datasets with results, or files in key-value store.
In Standby mode, an Actor provides a web server which can be used as a website, API, or an MCP server.

Apify vocabulary and the platform model are defined once, in the agent quickstart at https://apify.com/agents.md.

## How to integrate an Actor?

If asked about integration, you help developers integrate Actors into their projects.
You adapt to their stack and deliver integrations that are safe, well-documented, and production-ready.

Do not guess an integration path. Every one of them is in the agent quickstart at https://apify.com/agents.md: the Apify MCP server, Agent Skills with the Apify CLI, the JavaScript and Python clients, the REST API, and the account-free path for an agent with no human to sign in. It also carries the rule on stating cost before the first paid run.

For examples already wired to this Actor's own input schema, see the [API](#api) section below.

Each client library has reference documentation the quickstart does not restate: [JavaScript/TypeScript](https://docs.apify.com/api/client/js/docs.md) (`npm install apify-client`) and [Python](https://docs.apify.com/api/client/python/docs.md) (`pip install apify-client`).

# README

## Merge PDF API

Merge several PDFs from public URLs or file uploads into a single PDF. The combined size of all
input files can be up to **256 MB**. The result is written to the run's default key-value store as
`merged.pdf`, together with a machine-readable `OUTPUT` record.

The Actor uses an enterprise-grade PDF engine to copy every page into one document, preserving the
order of the input list. It is intended to be called through the Apify API or from Apify Console.

### Input

| Field | Type | Default | Description |
| --- | --- | --- | --- |
| `pdfUrls` | array of strings | Two sample PDFs | Public HTTP(S) URLs of the PDFs to merge, in output order. |
| `pdfFiles` | array of strings | - | Uploaded PDFs or Apify key-value store record URLs. Takes precedence over `pdfUrls`. |

Provide one or more PDFs. If both fields are empty, the Actor runs with two sample PDFs so the merge
can be tested immediately. When `pdfFiles` contains at least one file, the `pdfUrls` field is
ignored for that run.

For backwards compatibility, the legacy string fields `url` and `fileUpload` are still accepted when
the array fields are empty. New integrations should use `pdfUrls` and `pdfFiles`.

Only PDF input is accepted. URLs do not need to end in `.pdf`; the downloaded content is checked for
a PDF header before merging starts. Password-protected PDFs are rejected because their pages cannot
be read without the password. The combined size of all input PDFs must not exceed 256 MB.

### Output

The merged PDF is stored in the run's default key-value store under `merged.pdf` with content type
`application/pdf`.

When the run finishes, the **Output** tab in Apify Console lists the merged PDF and links to the
`OUTPUT` record. These links are defined in `.actor/output_schema.json`.

An `OUTPUT` JSON record describes the result:

```json
{
  "success": true,
  "message": "Merged 2 PDFs (5.1 MB, 12 pages) into one PDF (5.0 MB). The result is stored as \"merged.pdf\" in the run's key-value store.",
  "input": {
    "files": 2,
    "bytes": 5347738,
    "mb": "5.1 MB",
    "pages": 12,
    "sources": [
      {
        "source": "https://example.com/first.pdf",
        "filename": "first.pdf",
        "bytes": 3145728,
        "mb": "3.0 MB",
        "pages": 8
      },
      {
        "source": "https://example.com/second.pdf",
        "filename": "second.pdf",
        "bytes": 2202010,
        "mb": "2.1 MB",
        "pages": 4
      }
    ]
  },
  "output": {
    "key": "merged.pdf",
    "storeId": "STORE_ID",
    "filename": "merged.pdf",
    "contentType": "application/pdf",
    "bytes": 5242880,
    "mb": "5.0 MB",
    "pages": 12,
    "downloadUrl": "https://api.apify.com/v2/key-value-stores/STORE_ID/records/merged.pdf?signature=..."
  },
  "pricing": {
    "eventName": "pdf-mb",
    "unitPriceUsd": 0.001,
    "chargedEvents": 6,
    "estimatedCostUsd": 0.006,
    "charged": true,
    "actorStart": {
      "eventName": "apify-actor-start",
      "unitPriceUsd": 0.002,
      "events": 1,
      "estimatedCostUsd": 0.002,
      "chargedAutomatically": true
    },
    "estimatedTotalCostUsd": 0.008
  },
  "limits": {
    "memoryMb": 512,
    "maxMemoryMb": 512,
    "diskMb": 1024,
    "maxInputBytes": 268435456,
    "maxInputMb": 256
  }
}
```

On failure, `success` is `false`, `error.code` identifies the problem, and `error.message`
contains a user-facing explanation. The `OUTPUT` record is written for both successful and
failed runs.

#### Filename rules

The output key is always `merged.pdf`. Source filenames appear only in the `OUTPUT` metadata and
are sanitized before use with a cross-platform filename cleaner. Directory components are removed,
characters that are invalid in filenames are stripped, reserved device names are defused, and
trailing dots or spaces are removed. The remaining name is then normalized to letters, digits,
`.`, `_`, and `-`, and truncated to a safe length. For example, `hello world.pdf` becomes
`hello_world.pdf`.

### Pricing

The Actor uses **pay-per-event (PPE)** pricing with two charges.

#### Per-run fee

Apify charges the synthetic `apify-actor-start` event automatically at **$0.002 per start**
(**$2 per 1,000 runs**). It applies to every run, including runs that later fail, and is not
charged by the Actor code.

Because the Actor's memory is fixed at 512 MB, each run incurs exactly one start event ($0.002).

#### Per-MB fee

The Actor charges the event `pdf-mb` **once per started megabyte of the total input size**, at
**$0.001 per event**:

- 1 byte to 1 MB -> 1 event -> $0.001
- 5.1 MB total -> 6 events -> $0.006
- 128 MB total -> 128 events -> $0.128
- 256 MB total -> 256 events -> $0.256

This event is charged only after the merged PDF has been saved to the key-value store. Failed runs,
including oversized, non-PDF, and password-protected inputs, are not charged for `pdf-mb`.

#### Total cost

| Total input | Start fee | `pdf-mb` | Total |
| --- | --- | --- | --- |
| 1 byte to 1 MB | $0.002 | $0.001 | $0.003 |
| 5.1 MB | $0.002 | $0.006 | $0.008 |
| 128 MB | $0.002 | $0.128 | $0.130 |
| 256 MB | $0.002 | $0.256 | $0.258 |

The `pricing` object in `OUTPUT` reports both the `pdf-mb` charge and the automatic start fee.

### Size limits

The Actor runs with **512 MB of memory** and **1 GB of disk** (Apify gives each run disk space
equal to twice its memory). To leave headroom for the merge engine and the output file, the total
input limit is half the memory:

```text
max total input size = memory / 2 = 256 MB
```

| Memory | Disk | Maximum total input |
| --- | --- | --- |
| 512 MB (fixed) | 1 GB | 256 MB |

The Actor checks the remote `Content-Length` of every input before downloading. If a server does not
report a size, the same limit is enforced while streaming the download. An oversized set of files
produces an `OUTPUT` record with `error.code = "FILE_TOO_LARGE"` and no `pdf-mb` charge.

Files whose combined size exceeds 256 MB cannot be processed by this Actor; remove some files, use
smaller PDFs, or merge them in several runs. The default run timeout is **10 minutes**.

### Calling the API

Start an asynchronous run with a list of URLs:

```bash
curl -X POST "https://api.apify.com/v2/acts/OWNER~merge-pdf-api/runs?token=$APIFY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "pdfUrls": [
      "https://www.pdfpdf.com/samples/pptdemo1.pdf",
      "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf"
    ]
  }'
```

The response contains `data.id`, `data.defaultKeyValueStoreId`, and `data.status`. Poll the run,
then read the metadata and download the result:

```bash
curl "https://api.apify.com/v2/actor-runs/RUN_ID?token=$APIFY_TOKEN"

curl "https://api.apify.com/v2/key-value-stores/STORE_ID/records/OUTPUT?token=$APIFY_TOKEN"

curl -OJ "https://api.apify.com/v2/key-value-stores/STORE_ID/records/merged.pdf?token=$APIFY_TOKEN"
```

Synchronous call (waits for the run to finish):

```bash
curl -X POST "https://api.apify.com/v2/acts/OWNER~merge-pdf-api/run-sync?token=$APIFY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"pdfUrls":["https://example.com/first.pdf","https://example.com/second.pdf"]}'
```

Uploading files is also supported. Upload the PDFs to a key-value store, then pass their record URLs
as `pdfFiles`:

```bash
curl -X POST "https://api.apify.com/v2/acts/OWNER~merge-pdf-api/runs?token=$APIFY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "pdfFiles": [
      "https://api.apify.com/v2/key-value-stores/STORE_ID/records/first.pdf",
      "https://api.apify.com/v2/key-value-stores/STORE_ID/records/second.pdf"
    ]
  }'
```

### Error codes

| Code | Meaning |
| --- | --- |
| `INVALID_INPUT` | Missing/invalid URL list or unsupported scheme. |
| `DOWNLOAD_FAILED` | An input PDF could not be downloaded (DNS, TLS, HTTP 4xx/5xx, timeout). |
| `EMPTY_FILE` | One of the input sources returned an empty file. |
| `NOT_A_PDF` | One of the inputs is not a valid PDF or has no readable pages. |
| `PASSWORD_PROTECTED` | One of the PDFs is encrypted and needs a password. |
| `MERGE_FAILED` | The merge engine could not produce the merged PDF. |
| `UPLOAD_FAILED` | The result could not be written to the key-value store. |
| `FILE_TOO_LARGE` | The combined input exceeds the run's memory-derived limit. |
| `TEMP_DIR_FAILED` | The run could not create a temporary directory. |

# Actor input Schema

## `pdfUrls` (type: `array`):

Public HTTP(S) URLs of the PDFs to merge, in the order they should appear in the result. The default contains two sample PDFs for testing.

## `pdfFiles` (type: `array`):

Upload PDFs or paste Apify key-value store record URLs. When provided, these files take precedence over the PDF URLs field.

## Actor input object example

```json
{
  "pdfUrls": [
    "https://www.pdfpdf.com/samples/pptdemo1.pdf",
    "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf"
  ]
}
```

# Actor output Schema

## `mergedPdf` (type: `string`):

Contents of the run's default key-value store. The merged file is stored as merged.pdf with content type application/pdf.

## `result` (type: `string`):

JSON record describing the run: success flag, message, input files and sizes, total page count, output key, download URL, pricing, and limits. Failed runs set success to false and include error.code and error.message.

# API

You can run this Actor programmatically using our API. Below are code examples in JavaScript, Python, and CLI, as well as the OpenAPI specification and MCP server setup.

## JavaScript example

```javascript
import { ApifyClient } from 'apify-client';

// Initialize the ApifyClient with your Apify API token
// Replace the '<YOUR_API_TOKEN>' with your token
const client = new ApifyClient({
    token: '<YOUR_API_TOKEN>',
});

// Prepare Actor input
const input = {};

// Run the Actor and wait for it to finish
const run = await client.actor("api-center/merge-pdf-api").call(input);

// Fetch and print Actor results from the run's dataset (if any)
console.log('Results from dataset');
console.log(`💾 Check your data here: https://console.apify.com/storage/datasets/${run.defaultDatasetId}`);
const { items } = await client.dataset(run.defaultDatasetId).listItems();
items.forEach((item) => {
    console.dir(item);
});

// 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/js/docs

```

## Python example

```python
from apify_client import ApifyClient

# Initialize the ApifyClient with your Apify API token
# Replace '<YOUR_API_TOKEN>' with your token.
client = ApifyClient("<YOUR_API_TOKEN>")

# Prepare the Actor input
run_input = {}

# Run the Actor and wait for it to finish
run = client.actor("api-center/merge-pdf-api").call(run_input=run_input)

# Fetch and print Actor results from the run's dataset (if there are any)
print(f"💾 Check your data here: https://console.apify.com/storage/datasets/{run.default_dataset_id}")
for item in client.dataset(run.default_dataset_id).iterate_items():
    print(item)

# 📚 Want to learn more 📖? Go to → https://docs.apify.com/api/client/python/docs/quick-start

```

## CLI example

```bash
echo '{}' |
apify call api-center/merge-pdf-api --silent --output-dataset

```

## MCP server setup

```json
{
    "mcpServers": {
        "apify": {
            "type": "http",
            "url": "https://mcp.apify.com/?tools=fetch-actor-details,api-center/merge-pdf-api"
        }
    }
}
```

The hosted server signs you in with OAuth on first connect, so no API token belongs in this config. Clients without OAuth support can send an `Authorization: Bearer <APIFY_API_TOKEN>` header instead, using a token from API & Integrations in Apify Console (https://console.apify.com/settings/integrations).

## OpenAPI specification

Download the OpenAPI definition: https://api.apify.com/v2/actors/WZzAKlnSK0ul1Yydz/builds/u3XSH2I6NU8Hyu9OR/openapi.json