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.

wdthBuf.puh(entry.tStrng());
          }
        }
        hah.update(wdthBuf.jn());
      }
      f (cte) {
        hah.update("cteFnt");
        cnt cteWdth = dct.get("W") || t.get("W");
        f (Array.Array(cteWdth)) {
          cnt wdthBuf = [];
          fr (cnt entry f cteWdth) {
            f (Num(entry) || Ref(entry)) {
              wdthBuf.puh(entry.tStrng());
            } ele f (Array.Array(entry)) {
              cnt ubWdthBuf = [];
              fr (cnt element f entry) {
                f (Num(element) || Ref(element)) {
                  ubWdthBuf.puh(element.tStrng());
                }
              }
              wdthBuf.puh(`[${ubWdthBuf.jn()}]`);
            }
          }
          hah.update(wdthBuf.jn());
        }
        cnt cdTGdMap =
          dct.getRaw("CIDTGIDMap") || t.getRaw("CIDTGIDMap");
        f (cdTGdMap ntancef Name) {
          hah.update(cdTGdMap.name);
        } ele f (cdTGdMap ntancef Ref) {