We could use:
https://github.com/mozilla/pdf.js/blob/c3d08580627471432a6ad0b2fdb948df64126afa/src/display/api.js#L929

and look at bit 4.

The following pdf:
https://orimi.com/pdf-test.pdf
is not editable in neither Acrobat nor Edge nor Foxit and nor Okular.
};
      moreInfoButton.oncontextmenu = noContextMenuHandler;
      lessInfoButton.oncontextmenu = noContextMenuHandler;
      closeButton.oncontextmenu = noContextMenuHandler;
      moreInfoButton.hidden = false;
      lessInfoButton.hidden = true;
      Promise.all(moreInfoText).then(parts => {
        errorMoreInfo.value = parts.join("\n");
      });
    } else {
      Promise.all(moreInfoText).then(parts => {
        console.error(message + "\n" + parts.join("\n"));
      });
      this.fallback();
    }
  },
  progress(level) {
    if (this.downloadComplete) {
      
      
      return;
    }
    const percent = Math.round(level * 100);
    
    
    
    
    if (percent > this.loadingBar.percent || isNaN(percent)) {
      this.loadingBar.percent = percent;