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.

header31012 +
    format31012
  );
}
function validateOS2Table(os2, file) {
  file.pos = (file.start || 0) + os2.offset;
  const version = file.getUint16();
  
  
  file.skip(60); 
  const selection = file.getUint16();
  if (version < 4 && selection & 0x0300) {
    return false;
  }
  const firstChar = file.getUint16();
  const lastChar = file.getUint16();
  if (firstChar > lastChar) {
    return false;
  }
  file.skip(6); 
  const usWinAscent = file.getUint16();
  if (usWinAscent === 0) {
    
    return false;
  }
  
  os2.data[8] = os2.data[9] = 0; 
  return true;
}
function createOS2Table(properties, charstrings, override) {