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 loadingTask = getDocument(buildGetDocumentParams("issue6106.pdf"));
      const pdfDoc = await loadingTask.promise;
      const javascript = await pdfDoc.getJavaScript();
      expect(javascript).toEqual([
        "this.print({bUI:true,bSilent:false,bShrinkToFit:true});",
      ]);
      expect(javascript[0]).toMatch(AutoPrintRegExp);
      await loadingTask.destroy();
    });
    it("gets hasJSActions, in document without javaScript", async function () {
      const hasJSActions = await pdfDocument.hasJSActions();
      expect(hasJSActions).toEqual(false);
    });
    it("gets hasJSActions, in document with javaScript", async function () {
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")
      );
      const pdfDoc = await loadingTask.promise;
      const hasJSActions = await pdfDoc.hasJSActions();
      expect(hasJSActions).toEqual(true);
      await loadingTask.destroy();
    });
    it("gets non-existent JSActions", async function () {
      const jsActions = await pdfDocument.getJSActions();
      expect(jsActions).toEqual(null);
    });
    it("gets JSActions", async function () {
      
      const loadingTask = getDocument(
        buildGetDocumentParams("doc_actions.pdf")