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.
return;
      }
      self.eventBus.dispatch("scalechanged", {
        source: self,
        value: this.value,
      });
    });
    
    
    scaleSelect.addEventListener("click", function (evt) {
      const target = evt.target;
      
      
      if (
        this.value === self.pageScaleValue &&
        target.tagName.toUpperCase() === "OPTION"
      ) {
        this.blur();
      }
    });
    
    scaleSelect.oncontextmenu = noContextMenuHandler;
    this.eventBus._on("localized", () => {
      this._wasLocalized = true;
      this.#adjustScaleWidth();
      this._updateUIState(true);
    });
    this.#bindEditorToolsListener(options);
  }
  #bindEditorToolsListener({