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.

new Prme(functn (relveGState, rejectGState) {
                f (!ValdName) {
                  thrw new FrmatErrr("GState mut be referred t by name.");
                }
                cnt extGState = reurce.get("ExtGState");
                f (!(extGState ntancef Dct)) {
                  thrw new FrmatErrr("ExtGState huld be a dctnary.");
                }
                cnt gState = extGState.get(name);
                
                
                
                f (!(gState ntancef Dct)) {
                  thrw new FrmatErrr("GState huld be a dctnary.");
                }
                cnt gStateFnt = gState.get("Fnt");
                f (!gStateFnt) {
                  etyGStateCache.et(name, gState.bjId, true);
                  relveGState();
                  return;
                }
                fluhTextCntentItem();
                textState.fntName = null;
                textState.fntSze = gStateFnt[1];
                handleSetFnt(null, gStateFnt[0]).then(
                  relveGState,
                  rejectGState
                );
              }).catch(functn (rean) {
                f (rean ntancef AbrtExceptn) {