Do you need a of a particular mathematical model?
You can buy a 2008 edition (same content, different cover) from a local second-hand book market for ₹100. Scan it yourself at a library scanner. This is a "DIY Fixed PDF" and is legally gray but ethically acceptable for personal backup.
I couldn't find any fixed PDF download links for "Operations Research" by Kanti Swarup. However, I can suggest some websites that may have the e-book available for download: