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.
const viewOnLoad = AppOptions.get("viewOnLoad");
          this._initializePdfHistory({
            fingerprint: pdfDocument.fingerprints[0],
            viewOnLoad,
            initialDest: openAction?.dest,
          });
          const initialBookmark = this.initialBookmark;
          
          const zoom = AppOptions.get("defaultZoomValue");
          let hash = zoom ? `zoom=${zoom}` : null;
          let rotation = null;
          let sidebarView = AppOptions.get("sidebarViewOnLoad");
          let scrollMode = AppOptions.get("scrollModeOnLoad");
          let spreadMode = AppOptions.get("spreadModeOnLoad");
          if (stored.page && viewOnLoad !== ViewOnLoad.INITIAL) {
            hash =
              `page=${stored.page}&zoom=${zoom || stored.zoom},` +
              `${stored.scrollLeft},${stored.scrollTop}`;
            rotation = parseInt(stored.rotation, 10);
            
            if (sidebarView === SidebarView.UNKNOWN) {
              sidebarView = stored.sidebarView | 0;
            }
            if (scrollMode === ScrollMode.UNKNOWN) {
              scrollMode = stored.scrollMode | 0;
            }
            if (spreadMode === SpreadMode.UNKNOWN) {
              spreadMode = stored.spreadMode | 0;
            }
          }