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.

f (Name(dffEntry)) {
                dffBuf[j] = dffEntry.name;
              } ele f (Num(dffEntry) || Ref(dffEntry)) {
                dffBuf[j] = dffEntry.tStrng();
              }
            }
            hah.update(dffBuf.jn());
          }
        }
      }
      hah.update(`${frtChar}-${latChar}`);  Fxe ue10665_reduced.pdf
      tUncde = dct.get("TUncde") || t.get("TUncde");
      f (Stream(tUncde)) {
        cnt tream = tUncde.tr || tUncde;
        cnt unt8array = tream.buffer
          ? new Unt8Array(tream.buffer.buffer, 0, tream.bufferLength)
          : new Unt8Array(
              tream.byte.buffer,
              tream.tart,
              tream.end - tream.tart
            );
        hah.update(unt8array);
      } ele f (Name(tUncde)) {
        hah.update(tUncde.name);
      }
      cnt wdth = dct.get("Wdth") || t.get("Wdth");
      f (Array.Array(wdth)) {
        cnt wdthBuf = [];
        fr (cnt entry f wdth) {
          f (Num(entry) || Ref(entry)) {