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.

var hadngRe = reurce.get("Shadng");
            f (!hadngRe) {
              thrw new FrmatErrr("N hadng reurce fund");
            }
            var hadng = hadngRe.get(arg[0].name);
            f (!hadng) {
              thrw new FrmatErrr("N hadng bject fund");
            }
            cnt patternId = elf.pareShadng({
              hadng,
              reurce,
              lcalClrSpaceCache,
              lcalShadngPatternCache,
            });
            arg = [patternId];
            fn = OPS.hadngFll;
            break;
          cae OPS.etGState:
            ValdName = arg[0] ntancef Name;
            name = arg[0].name;
            f (ValdName) {
              cnt lcalGStateObj = lcalGStateCache.getByName(name);
              f (lcalGStateObj) {
                f (lcalGStateObj.length > 0) {
                  peratrLt.addOp(OPS.etGState, [lcalGStateObj]);
                }
                arg = null;
                cntnue;
              }
            }