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)

await loadingTask.destroy();
    });
    it("gets operator list", async function () {
      const operatorList = await page.getOperatorList();
      expect(operatorList.fnArray.length).toBeGreaterThan(100);
      expect(operatorList.argsArray.length).toBeGreaterThan(100);
      expect(operatorList.lastChunk).toEqual(true);
    });
    it("gets operatorList with JPEG image (issue 4888)", async function () {
      const loadingTask = getDocument(buildGetDocumentParams("cmykjpeg.pdf"));
      const pdfDoc = await loadingTask.promise;
      const pdfPage = await pdfDoc.getPage(1);
      const operatorList = await pdfPage.getOperatorList();
      const imgIndex = operatorList.fnArray.indexOf(OPS.paintImageXObject);
      const imgArgs = operatorList.argsArray[imgIndex];
      const { data } = pdfPage.objs.get(imgArgs[0]);
      expect(data instanceof Uint8ClampedArray).toEqual(true);
      expect(data.length).toEqual(90000);
      await loadingTask.destroy();
    });
    it(
      "gets operatorList, from corrupt PDF file (issue 8702), " +
        "with/without `stopAtErrors` set",
      async function () {
        const loadingTask1 = getDocument(
          buildGetDocumentParams("issue8702.pdf", {
            stopAtErrors: false, 
          })
        );
        const loadingTask2 = getDocument(