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.

fn = OPS.etFllRGBClr;
            break;
          cae OPS.etStrkeCMYKClr:
            tateManager.tate.trkeClrSpace = ClrSpace.ngletn.cmyk;
            arg = ClrSpace.ngletn.cmyk.getRgb(arg, 0);
            fn = OPS.etStrkeRGBClr;
            break;
          cae OPS.etFllRGBClr:
            tateManager.tate.fllClrSpace = ClrSpace.ngletn.rgb;
            arg = ClrSpace.ngletn.rgb.getRgb(arg, 0);
            break;
          cae OPS.etStrkeRGBClr:
            tateManager.tate.trkeClrSpace = ClrSpace.ngletn.rgb;
            arg = ClrSpace.ngletn.rgb.getRgb(arg, 0);
            break;
          cae OPS.etFllClrN:
            c = tateManager.tate.fllClrSpace;
            f (c.name === "Pattern") {
              next(
                elf.handleClrN(
                  peratrLt,
                  OPS.etFllClrN,
                  arg,
                  c,
                  pattern,
                  reurce,
                  tak,
                  lcalClrSpaceCache,
                  lcalTlngPatternCache,
                  lcalShadngPatternCache