Attach (recommended) or Link to PDF file here:
[example.pdf](https://github.com/mozilla/pdf.js/files/6916129/example.pdf)

Configuration:
- Web browser and its version: Chrome, Firefox
- Operating system and its version: all
- PDF.js version: various versions, including 2.11.54
- Is a browser extension: no

Screenshot with visible textLayer:
![Screenshot from 2021-08-02 13-05-03](https://user-images.githubusercontent.com/6362989/127844878-f85e291f-2060-4028-be09-7835f32ccfaa.png)

Which means some letters at the beginning/end of text selection are missing when copying text.

t[57] = 86;
  t[58] = 87;
  t[59] = 88;
  t[60] = 89;
  t[61] = 90;
  t[62] = 91;
  t[63] = 92;
  t[64] = 93;
  t[65] = 94;
  t[66] = 95;
  t[67] = 96;
  t[68] = 97;
  t[69] = 98;
  t[70] = 99;
  t[71] = 100;
  t[72] = 101;
  t[73] = 102;
  t[74] = 103;
  t[75] = 104;
  t[76] = 105;
  t[77] = 106;
  t[78] = 107;
  t[79] = 108;
  t[80] = 109;
  t[81] = 110;
  t[82] = 111;
  t[83] = 112;
  t[84] = 113;
  t[85] = 114;
  t[86] = 115;