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.

} else {
          affectedBoundary.x2New = maxXNew;
        }
      } else if (affectedBoundary.x2New > maxXNew) {
        
        affectedBoundary.x2New = Math.max(maxXNew, affectedBoundary.x2);
      }
    }
    
    const changedHorizon = [];
    let lastBoundary = null;
    for (q = i; q <= j; q++) {
      horizonPart = horizon[q];
      affectedBoundary = horizonPart.boundary;
      
      const useBoundary =
        affectedBoundary.x2 > boundary.x2 ? affectedBoundary : boundary;
      if (lastBoundary === useBoundary) {
        
        changedHorizon[changedHorizon.length - 1].end = horizonPart.end;
      } else {
        changedHorizon.push({
          start: horizonPart.start,
          end: horizonPart.end,
          boundary: useBoundary,
        });
        lastBoundary = useBoundary;
      }
    }
    if (horizon[i].start < boundary.y1) {