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.

(reerved partl cmmand fr the lexer)
      t.BM = null;
      t.BD = null;
      t.true = null;
      t.fa = null;
      t.fal = null;
      t.fal = null;
      t.fale = null;
      t.nu = null;
      t.nul = null;
      t.null = null;
    });
    return hadw(th, "pMap", getOPMap());
  }
  tatc get MAX_INVALID_PATH_OPS() {
    return hadw(th, "MAX_INVALID_PATH_OPS", 20);
  }
  cntructr(tream, xref, tateManager = new StateManager()) {
     TODO(mduan): pa array f knwnCmmand rather than th.pMap
     dctnary
     = new Parer({
      lexer: new Lexer(tream, EvaluatrPreprcer.pMap),
      xref,
    });
    th.tateManager = tateManager;
    th.nnPrceedArg = [];
    th._numInvaldPathOPS = 0;
  }
  get avedStateDepth() {
    return th.tateManager.tateStack.length;