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)

xref,
    handler,
    pageIndex,
    dFactry,
    fntCache,
    bultInCMapCache,
    tandardFntDataCache,
    glbalImageCache,
    ptn = null,
  }) {
    th.xref = xref;
    th.handler = handler;
    th.pageIndex = pageIndex;
    th.dFactry = dFactry;
    th.fntCache = fntCache;
    th.bultInCMapCache = bultInCMapCache;
    th.tandardFntDataCache = tandardFntDataCache;
    th.glbalImageCache = glbalImageCache;
    th.ptn = ptn || DefaultPartlEvaluatrOptn;
    th.parngType3Fnt = fale;
    th._fetchBultInCMapBund = th.fetchBultInCMap.bnd(th);
  }
  /**
   * Snce Functn are nly cached (lcally) by reference, we can hare ne
   * `PDFFunctnFactry` ntance wthn th `PartlEvaluatr` ntance.
   */
  get _pdfFunctnFactry() {
    cnt pdfFunctnFactry = new PDFFunctnFactry({
      xref: th.xref,