.jdf is a JEOL file, and you can open it by clicking the button with three horizontal lines at the top left and then 'open'. Under options select "Open NMR data stored in special formats", and set File type to 'JNMR'. Then just click 'ok' and navigate to the file you want to open.
It is helpful to execute this command while another data set is open. Otherwise there are problems with stoing the converted data set. if the jdf file is digitally filtered data use PHC1 of ~ 6900
To open files in Bruker TopSpin, it's essential to save them in a format compatible with the software. If you haven't already, download the Delta software from https://www.jeolusa.com/PRODUCTS/Nuclear-Magnetic-Resonance/Delta-NMR-Software. Once you have the Delta software, save your files in formats supported by TopSpin (Bruker). Also read post https://www.chemistryabc.com/jdf-files-opening-jeol-files-with-nmr-data-in-topspin/