Before hunting for a download link, it is crucial to understand why this book dominates the market.
Instead of searching for a risky "free download," consider these legal, low-cost options that provide the same "top" quality content.
The National Digital Library of India (ndl.iitkgp.ac.in) has partnered with various universities. If you have a student ID, you can often access the 6th or 7th edition of P. D. Sharma for free in a controlled digital lending format.
While the demand for the "free download" is understandable, the feature would be incomplete without a note on the quality of that download.
Most PDF versions circulating the web are scanned copies of older editions. They often miss the clarity of the diagrams—diagrams that are crucial for understanding ecological pyramids or biogeochemical cycles. Furthermore, ecology is a dynamic field. Issues like climate change policies, carbon trading, and recent international protocols evolve rapidly. A scanned PDF from 2015 might give you the history of the problem, but it won't have the latest data required for a top-tier rank today.