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.constructor === BaseViewer) {
      throw new Error("Cannot initialize BaseViewer.");
    }
    const viewerVersion =
      typeof PDFJSDev !== "undefined" ? PDFJSDev.eval("BUNDLE_VERSION") : null;
    if (version !== viewerVersion) {
      throw new Error(
        `The API version "${version}" does not match the Viewer version "${viewerVersion}".`
      );
    }
    this.container = options.container;
    this.viewer = options.viewer || options.container.firstElementChild;
    if (
      typeof PDFJSDev === "undefined" ||
      PDFJSDev.test("!PRODUCTION || GENERIC")
    ) {
      if (
        !(
          this.container?.tagName.toUpperCase() === "DIV" &&
          this.viewer?.tagName.toUpperCase() === "DIV"
        )
      ) {
        throw new Error("Invalid `container` and/or `viewer` option.");
      }
      if (