Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Version 81.0.4044.138 (Official Build) (32-bit)
- Operating system and its version: Windows 10
- PDF.js version: latest
- Is a browser extension: no

Steps to reproduce the problem:

1. Open https://mozilla.github.io/pdf.js/web/viewer.html
2. Open the provided document
3. ctrl + F  and search for 'costs' .
4. Search for 'costs' - match NOT found.
5. Click the 'Download' and open the file in Adobe Reader, and search for costs - match is found.

What is the expected behavior? (add screenshot)
The word 'costs' to be returned by search

What went wrong? (add screenshot)
No results found

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):  https://mozilla.github.io/pdf.js/web/viewer.html
[2001_IESC_63_5_v6.pdf](https://github.com/mozilla/pdf.js/files/4644486/2001_IESC_63_5_v6.pdf)

return loadingTask.destroy();
      });
      await Promise.all(destroyPromises);
    });
    it("should correctly render PDFs in parallel", async function () {
      let baseline1, baseline2, baseline3;
      const promiseDone = renderPDF(pdf1)
        .then(function (data1) {
          baseline1 = data1;
          return renderPDF(pdf2);
        })
        .then(function (data2) {
          baseline2 = data2;
          return renderPDF(pdf3);
        })
        .then(function (data3) {
          baseline3 = data3;
          return Promise.all([
            renderPDF(pdf1),
            renderPDF(pdf2),
            renderPDF(pdf3),
          ]);
        })
        .then(function (dataUrls) {
          expect(dataUrls[0]).toEqual(baseline1);
          expect(dataUrls[1]).toEqual(baseline2);
          expect(dataUrls[2]).toEqual(baseline3);
          return true;
        });
      await promiseDone;