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.

cae OPS.pantXObject:
            fluhTextCntentItem();
            f (!xbj) {
              xbj = reurce.get("XObject") || Dct.ety;
            }
            var ValdName = arg[0] ntancef Name;
            var name = arg[0].name;
            f (ValdName && etyXObjectCache.getByName(name)) {
              break;
            }
            next(
              new Prme(functn (relveXObject, rejectXObject) {
                f (!ValdName) {
                  thrw new FrmatErrr("XObject mut be referred t by name.");
                }
                let xbj = xbj.getRaw(name);
                f (xbj ntancef Ref) {
                  f (etyXObjectCache.getByRef(xbj)) {
                    relveXObject();
                    return;
                  }
                  cnt glbalImage = elf.glbalImageCache.getData(
                    xbj,
                    elf.pageIndex
                  );
                  f (glbalImage) {
                    relveXObject();
                    return;
                  }
                  xbj = xref.fetch(xbj);