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.
if (!this.pdfDocument) {
      return;
    }
    if (!labels) {
      this._pageLabels = null;
    } else if (
      !(Array.isArray(labels) && this.pdfDocument.numPages === labels.length)
    ) {
      this._pageLabels = null;
      console.error(`setPageLabels: Invalid page labels.`);
    } else {
      this._pageLabels = labels;
    }
    
    for (let i = 0, ii = this._pages.length; i < ii; i++) {
      this._pages[i].setPageLabel(this._pageLabels?.[i] ?? null);
    }
  }
  _resetView() {