Since this is a religious text often published by local Kerala-based publishers, you can find digital versions using these specific search terms:
Reciting the Muhiyudheen Ratheeb is believed to offer several spiritual and worldly advantages: muhiyudheen ratheeb pdf
Because the Ratheeb contains thousands of Salawat, the Prophet ﷺ has promised that those who send abundant blessings upon him will receive his intercession. Since this is a religious text often published