PDF files:
[1.pdf](https://github.com/mozilla/pdf.js/files/2955999/1.pdf)
[2.pdf](https://github.com/mozilla/pdf.js/files/2956000/2.pdf)
[3.pdf](https://github.com/mozilla/pdf.js/files/2956002/3.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: Ubuntu, macOS
- PDF.js version: 2.2.42, but the same was with 2.1.x, and with https://mozilla.github.io/pdf.js/web/viewer.html
- Is a browser extension: no

Steps to reproduce the problem:
1. Select text
2. Copy text

What went wrong?

Getting this:
`OpenSansisahumanistsansseriftypefacedesignedbySteveMatteson.OpenSanswasdesignedwithanuprightstress,openformsandaneu-tral,yetfriendlyappearance.Itwasoptimizedforprint,web,andmobileinterfaces,andhasexcellentlegibilitycharacteristicsinitsletterforms(seefigureonthefollowingpage).ThisfontisavailablefromtheGoogleFontDirectory[]asTrueTypefileslicensedundertheApacheLicenseversion..`

Instead of this:
`Open Sans is a humanist sans serif typeface designed by Steve Matteson.
Open Sans was designed with an upright stress, open forms and a neutral,
yet friendly appearance. It was optimized for print, web, and mobile
interfaces, and has excellent legibility characteristics in its letterforms (see
figure 1 on the following page). This font is available from the Google Font
Directory [1] as TrueType files licensed under the Apache License version 2.0.`

This is quite significant problem, because I would say 1/20 of scientific papers encounter this problem.

b.y1 = width - e.right;
    b.x2 = box.bottom;
    b.y2 = width - e.left;
    b.index = i;
    b.x1New = undefined;
    b.x2New = undefined;
  });
  expandBoundsLTR(height, bounds);
  for (const b of bounds) {
    const i = b.index;
    expanded[i].top = b.x1New;
    expanded[i].bottom = b.x2New;
  }
  return expanded;
}
function expandBoundsLTR(width, bounds) {
  
  bounds.sort(function (a, b) {
    return a.x1 - b.x1 || a.index - b.index;
  });
  
  const fakeBoundary = {
    x1: -Infinity,
    y1: -Infinity,
    x2: 0,
    y2: Infinity,
    index: -1,
    x1New: 0,
    x2New: 0,
  };