A PDF can have other files attached to it. This might not be apparent when we’re viewing PDF files in the browser, however many PDF viewers have this feature to extract and display PDF attachment files.

For example, let’s consider this file URL. When this URL is opened in the browser, we’re only able to view PDF contents like below.

However, when the same file is opened in software like Foxit PDF Reader attachments are visible.

The main goal of this tutorial is to demonstrate how to extract PDF attachments programmatically. PDF.co API Endpoint “v1/pdf/attachments/extract” just do this job. Also, we’ll be using NodeJs to demonstrate source code.

Let’s dive into the source code first, then we’ll analyze it!

Source Code

var https = require("https");
var fs = require("fs");
var path = require("path");

// The authentication key (API Key).
// Get your own by registering at https://app.pdf.co
const API_KEY = "***********************************";


// Source PDF file
// You can also upload your own file into PDF.co and use it as url. Check "Upload File" samples for code snippets: https://github.com/bytescout/pdf-co-api-samples/tree/master/File%20Upload/    
const SourceFileUrl = "https://bytescout-com.s3.us-west-2.amazonaws.com/files/demo-files/cloud-api/pdf-attachments/attachments.pdf";


// Prepare request for API endpoint
var queryPath = `/v1/pdf/attachments/extract`;

// JSON payload for api request
var jsonPayload = JSON.stringify({
    url: SourceFileUrl
});

var reqOptions = {
    host: "api.pdf.co",
    method: "POST",
    path: queryPath,
    headers: {
        "x-api-key": API_KEY,
        "Content-Type": "application/json",
        "Content-Length": Buffer.byteLength(jsonPayload, 'utf8')
    }
};
// Send request
var postRequest = https.request(reqOptions, (response) => {
    response.on("data", (d) => {
        // Parse JSON response
        var data = JSON.parse(d);
        if (data.error == false) {
            // Download extracted files
            data.urls.forEach((url) => {
                var localFileName = path.basename(url);
                var file = fs.createWriteStream(localFileName);
                https.get(url, (response2) => {
                    response2.pipe(file)
                        .on("close", () => {
                            console.log(`Generated file saved as "${localFileName}" file.`);
                        });
                });
            }, this);
        }
        else {
            // Service reported error
            console.log(data.message);
        }
    });
}).on("error", (e) => {
    // Request error
    console.error(e);
});

// Write request data
postRequest.write(jsonPayload);
postRequest.end();

Output

The following animation demonstrates that the source code is extracting PDF attachments and downloading/storing them to the same directory.

Analysis

Now that we’ve already viewed the source code and its output GIF, let’s highlight important code snippets.

As previously mentioned, PDF.co endpoint “v1/pdf/attachments/extract” is being used for PDF attachment extraction.

// Prepare request for API endpoint
var queryPath = `/v1/pdf/attachments/extract`;

Furthermore, PDF.co API Key is passed into the request header. This API key is required for request authentication.

var reqOptions = {
    host: "api.pdf.co",
    method: "POST",
    path: queryPath,
    headers: {
        "x-api-key": API_KEY,

We can obtain this API key by signing-up with PDF.co.

The rest of the code is simply invoking the PDF.co endpoint, obtaining the resulting JSON, downloading URLs, and saving them as separate files.

Useful Links

I hope this article is useful to you. Please try this out for better exposure. Thank you!

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