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 renderTask = pdfPage.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
      });
      expect(renderTask instanceof RenderTask).toEqual(true);
      
      renderTask.onContinue = function (cont) {
        waitSome(cont);
      };
      try {
        await pdfDoc.cleanup();
        
        expect(false).toEqual(true);
      } catch (reason) {
        expect(reason instanceof Error).toEqual(true);
        expect(reason.message).toEqual(
          "startCleanup: Page 1 is currently rendering."
        );
      }
      await renderTask.promise;
      CanvasFactory.destroy(canvasAndCtx);
      await loadingTask.destroy();
    });
    it("caches image resources at the document/page level as expected (issue 11878)", async function () {
      const { NUM_PAGES_THRESHOLD } = GlobalImageCache,
        EXPECTED_WIDTH = 2550,
        EXPECTED_HEIGHT = 3300;
      const loadingTask = getDocument(buildGetDocumentParams("issue11878.pdf"));
      const pdfDoc = await loadingTask.promise;