Open PDFs in a Next.js App with PSPDFKit

Next.js is a JavaScript framework created by ZEIT that lets you build server-side rendered and static web applications using React. It has many great features and advantages, which might make Next.js your first option for building your next web application.

In this blog post, we will show you how to open a PDF in your Next.js application in a matter of minutes.

Setting Up Next.js

We can use create-next-app to start a new Next.js project by running the following:

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npm i -g create-next-app
create-next-app

It will ask for the project name and create a directory with that name. Once inside that directory, we can run npm run dev to start the development server, and we can load the page on http://localhost:3000. Now our next goal is to integrate PSPDFKit into our application.

Integrating PSPDFKit

The first thing we will need before integrating PSPDFKit into our application is the license key. If you are not an existing customer, you can easily obtain a free trial license key. Once we have the license key, we have to make its value accessible in the app. For this, we will pass a custom configuration to the Next.js application.

We can create a file named license-key at the root and then pass PSPDFKIT_LICENSE_KEY as an environment variable to make sure its value is available to our web app. To do this, we will have to create a new file named next.config.js (Next.js’ custom configuration) at the root of the project folder where package.json is located. The code will look like this:

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// next.config.js

const webpack = require("webpack");
const fs = require("fs");

const licenseKey = fs
  .readFileSync("./license-key")
  .toString()
  .replace(/\s/g, "");

module.exports = {
  env: {
    PSPDFKIT_LICENSE_KEY: licenseKey
  }
};

When we run the build after creating this file, webpack replaces all occurrences of process.env.PSPDFKIT_LICENSE_KEY in our app with their respective values at the build time. Now we can use the new license key to initialize PSPDFKit for Web.

In order for PSPDFKit for Web to work, we also have to copy the directory containing all the required library files (artifacts) to the public folder. We can use the following command to do this:

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cp -R ./node_modules/pspdfkit/dist/pspdfkit-lib ./public
ls ./public # -> pspdfkit-lib

Alternatively, we can add the copy command as a postinstall hook in package.json:

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{
  "scripts": {
    "dev": "next dev",
    "start": "next start",
    "build": "next build",
    "postinstall": "cp -R ./node_modules/pspdfkit/dist/pspdfkit-lib ./public"
  }
}

This means that every time we install the pspdfkit package from npm, the pspdfkit-lib directory will automatically get copied from the node_modules folder to the public folder.

By default, PSPDFKit assumes that the assets folder is present in the same folder of our application module, but in our case, we have kept it inside the public folder, so we will have to pass a baseUrl option while initializing PSPDFKit. In pages/index.js, we will load PSPDFKit with the required options (to view all the options, visit our API documentation). Make sure you put your PDF file (in this case, example.pdf) in the public folder too. Now we are ready to initialize PSPDFKit in pages/index.js:

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// pages/index.js

import React, { useEffect } from "react";

export default function() {
  const containerRef = useRef(null);

  useEffect(() => {
    let instance, PSPDFKit;
    (async function() {
      PSPDFKit = await import("pspdfkit");
      instance = await PSPDFKit.load({
        container: containerRef.current,
        document: "/example.pdf",
        licenseKey: process.env.PSPDFKIT_LICENSE_KEY,
        baseUrl: `${window.location.protocol}//${window.location.host}/`
      });
    })();

    return () => PSPDFKit && PSPDFKit.unload(containerRef.current);
  }, []);

  return <div ref={containerRef} style={{ height: "100vh"}}/>
  );
}

In the snippet above, PSPDFKit.load is called with a configuration object where we define:

• baseUrl, which is where our assets are available.
• pdf, which is the relative URL for our example PDF file. You can also pass the ArrayBuffer of our file.
• container, which is where we mount PSPDFKit.
• licenseKey, which is where we write your license key.

The above code uses Hooks. In case you are not familiar with Hooks, you can read about them on the official React website.

We asynchronously import PSPDFKit inside of a useEffect hook after the page has mounted. This way, we ensure that our initial bundle size is not large, thereby resulting in better perceived load time and the library loading only on the browser (since PSPDFKit is a client-side library).

Opening a Local PDF

PSPDFKit for Web can also open local PDF files. In such a case, the pdf configuration option should be an ArrayBuffer of our file.

To open a file, we need to create a file picker and, when selecting a file, convert it to ArrayBuffer using the FileReader API (see an example here).

Once we have the PDF in the ArrayBuffer format, we can call PSPDFKit.load with it.

Wrapping Up

Our final folder structure will look like this:

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pspdfkit-next-js-example
├─ license-key
├─ next.config.js
├─ package.json
├─ pages
│  └─ index.js
├─ public
│  ├─ example.pdf
│  └─ pspdfkit-lib
└─ yarn.lock

We can now start the server by running npm run dev, and if everything works as expected, we will be able to see PSPDFKit running at http://localhost:3000.

You can find the source code of this example on GitHub.

Conclusion

With just a few lines of code, we were able to utilize the full power of PSPDFKit in a Next.js application. This is a great way to get started with handling PDFs inside a Next.js application.

PSPDFKit for Web can help you add advanced PDF capabilities to your app. Together with PSPDFKit Instant, we offer an enterprise-ready PDF solution for web browsers and other platforms, along with industry-leading first-class support included with every plan. Check out our demo to see PSPDFKit for Web in action.