Yes, you can find this PDF floating around on VK, Telegram, and various archive sites. Many students do.
But there is a catch. The full LGSWE is a 1,204-page beast. It is expensive, heavy, and reads like a doctoral thesis. longman student grammar of spoken and written english pdf vk
While the temptation to grab a free PDF from VK is real, consider supporting the authors or finding a legal second-hand copy. Your English level (and your conscience) will thank you. Yes, you can find this PDF floating around