If you type the keyword into a search engine, you will find a mix of results. Unfortunately, none will lead you to a single, complete, unbroken PDF of the entire work. Here is why:
If you are a student or professor, log into your university library portal. Search for the "Sangita Ratnakara" within JSTOR, Project MUSE, or (a repository of Indian theses). Many doctoral dissertations include the full English translation as an appendix, which you can legally download as a PDF. sangita ratnakara english translation pdf