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.

const numPages = pdfDoc.numPages;
      expect(numPages).toEqual(3);
      const viewPromises = [];
      for (let i = 0; i < numPages; i++) {
        viewPromises[i] = pdfDoc.getPage(i + 1).then(pdfPage => {
          return pdfPage.view;
        });
      }
      const [page1, page2, page3] = await Promise.all(viewPromises);
      expect(page1).toEqual([0, 0, 612, 792]);
      expect(page2).toEqual([0, 0, 800, 600]);
      expect(page3).toEqual([0, 0, 600, 800]);
      await viewLoadingTask.destroy();
    });
    it("gets viewport", function () {
      const viewport = page.getViewport({ scale: 1.5, rotation: 90 });
      expect(viewport.viewBox).toEqual(page.view);
      expect(viewport.scale).toEqual(1.5);
      expect(viewport.rotation).toEqual(90);
      expect(viewport.transform).toEqual([0, 1.5, 1.5, 0, 0, 0]);
      expect(viewport.width).toEqual(1262.835);
      expect(viewport.height).toEqual(892.92);
    });
    it('gets viewport with "offsetX/offsetY" arguments', function () {
      const viewport = page.getViewport({
        scale: 1,
        rotation: 0,
        offsetX: 100,
        offsetY: -100,
      });