The Printer's Marks tutorial (https://helpx.adobe.com/indesign/using/printers-marks-bleeds.html) says: If you select the Crop Marks option, fold marks are printed as solid lines when spreads are printed. But there is no detail about how to create fold marks, and simply printing crop marks does not appear to automatically create fold marks or offer any option to do so. More clarity and specifics would be helpful.