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)

changedHorizon[0].start = boundary.y1;
      changedHorizon.unshift({
        start: horizon[i].start,
        end: boundary.y1,
        boundary: horizon[i].boundary,
      });
    }
    if (boundary.y2 < horizon[j].end) {
      changedHorizon[changedHorizon.length - 1].end = boundary.y2;
      changedHorizon.push({
        start: boundary.y2,
        end: horizon[j].end,
        boundary: horizon[j].boundary,
      });
    }
    
    
    
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      if (affectedBoundary.x2New !== undefined) {
        continue;
      }
      let used = false;
      for (
        k = i - 1;
        !used && k >= 0 && horizon[k].start >= affectedBoundary.y1;
        k--
      ) {