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.promise
          .then(function (pdf) {
            return pdf.destroy();
          })
          .then(
            function () {
              expect(expectSuccess).toEqual(true);
            },
            function (error) {
              if (expectSuccess) {
                
                expect(error).toEqual("There should not be any error");
              }
              expect(expectSuccess).toEqual(false);
            }
          );
      }
      function testCanLoad(filename, options) {
        return _checkCanLoad(true, filename, options);
      }
      function testCannotLoad(filename, options) {
        return _checkCanLoad(false, filename, options);
      }
      afterEach(async function () {
        if (loadingTask && !loadingTask.destroyed) {
          await loadingTask.destroy();
        }
      });
      it("server disallows cors", async function () {
        await testCannotLoad("basicapi.pdf");