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[1] = 32;
  t[4] = 65;
  t[6] = 193;
  t[17] = 66;
  t[18] = 67;
  t[21] = 268;
  t[24] = 68;
  t[28] = 69;
  t[30] = 201;
  t[32] = 282;
  t[38] = 70;
  t[39] = 71;
  t[44] = 72;
  t[47] = 73;
  t[49] = 205;
  t[58] = 74;
  t[60] = 75;
  t[62] = 76;
  t[68] = 77;
  t[69] = 78;
  t[75] = 79;
  t[87] = 80;
  t[89] = 81;
  t[90] = 82;
  t[92] = 344;
  t[94] = 83;
  t[97] = 352;
  t[100] = 84;
  t[104] = 85;
  t[115] = 86;