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)

expect(viewport.transform).toEqual([1, 0, 0, -1, 100, 741.89]);
    });
    it('gets viewport respecting "dontFlip" argument', function () {
      const scale = 1,
        rotation = 0;
      const viewport = page.getViewport({ scale, rotation });
      const dontFlipViewport = page.getViewport({
        scale,
        rotation,
        dontFlip: true,
      });
      expect(dontFlipViewport).not.toEqual(viewport);
      expect(dontFlipViewport).toEqual(viewport.clone({ dontFlip: true }));
      expect(viewport.transform).toEqual([1, 0, 0, -1, 0, 841.89]);
      expect(dontFlipViewport.transform).toEqual([1, 0, -0, 1, 0, 0]);
    });
    it("gets viewport with invalid rotation", function () {
      expect(function () {
        page.getViewport({ scale: 1, rotation: 45 });
      }).toThrow(
        new Error(
          "PageViewport: Invalid rotation, must be a multiple of 90 degrees."
        )
      );
    });
    it("gets annotations", async function () {
      const defaultPromise = page.getAnnotations().then(function (data) {
        expect(data.length).toEqual(4);
      });
      const anyPromise = page