How to render a PDF with React

June 2, 2022

There’s a fantastic React library aptly named react-pdf for rendering PDFs on a website.

However, when using it, I kept running into issues. For example, my PDF would constantly just say:

Failed to load PDF file.

Eventually I figured it out, and I wanted to share how I got react-pdf working.

First, install react-pdf:

npm install react-pdf

Here’s an example of the component using react-pdf that I ended up writing:

import { useState, useEffect, useRef } from "react";
import { Document, Page, pdfjs } from "react-pdf";

pdfjs.GlobalWorkerOptions.workerSrc = `https://unpkg.com/pdfjs-dist@${pdfjs.version}/build/pdf.worker.min.js`;

export default function PDF({ src }) {
  const container = useRef(null);

  const [width, setWidth] = useState(0);
  useEffect(() => {
    setWidth(container.current.clientWidth);
  }, []);

  const [numPages, setNumPages] = useState(0);

  return (
    <>
      <div ref={container}>
        <Document
          file={src}
          onLoadSuccess={({ numPages }) => setNumPages(numPages)}
          onLoadError={console.error}
        >
          {Array.from(new Array(numPages)).map((_, i) => (
            <Page pageNumber={i + 1} width={width} key={i} />
          ))}
        </Document>
      </div>
    </>
  );
}
  • One of the trickiest things to get working is the workerSrc, which is a URL to a JavaScript “worker” that renders the PDF. This is a part of pdf.js, the powerful underlying library used by react-pdf. react-pdf was looking for a file at /pdf.worker.js, which didn’t exist. Eventually I solved the problem by pointing the package towards a version of pdf.worker.js on unpkg, a website that hosts npm packages.
  • I measure the wrapping container when the page loads and set the PDF’s page width to the correct width.
  • When the PDF loads, I take the number of pages that it has and show all the pages. You can also just show one page at a time by rendering a single <Page /> component and changing the pageNumber, but I wanted to show the full PDF on the website.
    • Array.from(new Array(numPages)) is just a fancy way of creating an array of length numPages where each slot in the array is empty.
  • Defining onLoadError can be very helpful for debugging, since by default these messages aren’t printed to the console.