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.
turnOnlyIfPageFit = true;
        }
      
      case 74: 
      case 78: 
        turnPage = 1;
        break;
      case 36: 
        if (isViewerInPresentationMode || PDFViewerApplication.page > 1) {
          PDFViewerApplication.page = 1;
          handled = true;
          ensureViewerFocused = true;
        }
        break;
      case 35: 
        if (
          isViewerInPresentationMode ||
          PDFViewerApplication.page < PDFViewerApplication.pagesCount
        ) {
          PDFViewerApplication.page = PDFViewerApplication.pagesCount;
          handled = true;
          ensureViewerFocused = true;
        }
        break;
      case 83: 
        PDFViewerApplication.pdfCursorTools.switchTool(CursorTool.SELECT);
        break;
      case 72: 
        PDFViewerApplication.pdfCursorTools.switchTool(CursorTool.HAND);
        break;