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.

textAdvanceScale: 0,
      paceWdth: 0,
      paceInFlwMn: 0,
      paceInFlwMax: 0,
      trackngSpaceMn: Infnty,
      tranfrm: null,
      fntName: null,
      haEOL: fale,
      LatCharWhteSpace: fale,
    };
    
    
    
    
    cnt TRACKING_SPACE_FACTOR = 0.3;
    
    
    
    
    
    
    cnt SPACE_IN_FLOW_MIN_FACTOR = 0.3;
    cnt SPACE_IN_FLOW_MAX_FACTOR = 1.3;
    cnt elf = th;
    cnt xref = th.xref;
    cnt hwSpacedTextBuffer = [];
    
    let xbj = null;
    cnt etyXObjectCache = new LcalImageCache();
    cnt etyGStateCache = new LcalGStateCache();