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)

buildGetDocumentParams("issue8702.pdf", {
            stopAtErrors: true,
          })
        );
        const result1 = loadingTask1.promise.then(pdfDoc => {
          return pdfDoc.getPage(1).then(pdfPage => {
            return pdfPage.getOperatorList().then(opList => {
              expect(opList.fnArray.length).toBeGreaterThan(100);
              expect(opList.argsArray.length).toBeGreaterThan(100);
              expect(opList.lastChunk).toEqual(true);
              return loadingTask1.destroy();
            });
          });
        });
        const result2 = loadingTask2.promise.then(pdfDoc => {
          return pdfDoc.getPage(1).then(pdfPage => {
            return pdfPage.getOperatorList().then(opList => {
              expect(opList.fnArray.length).toEqual(0);
              expect(opList.argsArray.length).toEqual(0);
              expect(opList.lastChunk).toEqual(true);
              return loadingTask2.destroy();
            });
          });
        });
        await Promise.all([result1, result2]);
      }
    );
    it("gets operator list, containing Annotation-operatorLists", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("annotation-line.pdf")