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)

const renderTask1 = page.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
        optionalContentConfigPromise,
      });
      expect(renderTask1 instanceof RenderTask).toEqual(true);
      const renderTask2 = page.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
        optionalContentConfigPromise,
      });
      expect(renderTask2 instanceof RenderTask).toEqual(true);
      await Promise.all([
        renderTask1.promise,
        renderTask2.promise.then(
          () => {
            
            expect(false).toEqual(true);
          },
          reason => {
            
            expect(/multiple render\(\)/.test(reason.message)).toEqual(true);
          }
        ),
      ]);
    });
    it("cleans up document resources after rendering of page", async function () {
      const loadingTask = getDocument(buildGetDocumentParams(basicApiFileName));