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 this.isInPresentationMode
      ? false
      : this.container.scrollWidth > this.container.clientWidth;
  }
  get isVerticalScrollbarEnabled() {
    return this.isInPresentationMode
      ? false
      : this.container.scrollHeight > this.container.clientHeight;
  }
  _getVisiblePages() {
    const views =
        this._scrollMode === ScrollMode.PAGE
          ? this.#scrollModePageState.pages
          : this._pages,
      horizontal = this._scrollMode === ScrollMode.HORIZONTAL,
      rtl = horizontal && this._isContainerRtl;
    return getVisibleElements({
      scrollEl: this.container,
      views,
      sortByVisibility: true,
      horizontal,
      rtl,
    });
  }
  /**
   * @param {number} pageNumber
   */
  isPageVisible(pageNumber) {