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)

expectedStreamTypes[StreamType.FLATE] = true;
      const expectedFontTypes = {};
      expectedFontTypes[FontType.TYPE1STANDARD] = true;
      expectedFontTypes[FontType.CIDFONTTYPE2] = true;
      expect(stats).toEqual({
        streamTypes: expectedStreamTypes,
        fontTypes: expectedFontTypes,
      });
    });
    it("gets page stats after parsing page, without `pdfBug` set", async function () {
      await page.getOperatorList();
      expect(page.stats).toEqual(null);
    });
    it("gets page stats after parsing page, with `pdfBug` set", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams(basicApiFileName, { pdfBug: true })
      );
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      await pdfPage.getOperatorList();
      const stats = pdfPage.stats;
      expect(stats instanceof StatTimer).toEqual(true);
      expect(stats.times.length).toEqual(1);
      const [statEntry] = stats.times;
      expect(statEntry.name).toEqual("Page Request");
      expect(statEntry.end - statEntry.start).toBeGreaterThanOrEqual(0);
      await loadingTask.destroy();
    });
    it("gets page stats after rendering page, with `pdfBug` set", async function () {
      const loadingTask = getDocument(