webpack5 pdfjs

    if (!window.pdfjsLib) {
      let rawModule = await import('raw-loader!pdfjs-dist/build/pdf.min.js');
      let link = await import('file-loader!pdfjs-dist/build/pdf.worker.min.js');
      eval.call(null, rawModule.default);
      window.pdfjsLib.GlobalWorkerOptions.workerSrc = link.default;
    }

webpack < 5
https://github.com/mozilla/pdf.js/blob/master/examples/webpack/README.md