The internet is a cesspool of "copy-paste Gurus." Many free PDFs are cut-and-paste jobs from Wikipedia, mixed with poorly translated Kama Sutra excerpts. Worse, some contain dangerous advice regarding breath retention or energy work without proper safety disclaimers. You wouldn't learn surgery from a PDF; you shouldn’t learn advanced pranayama from one either.
Most of the PDFs floating around on blogspot, archive.org, or shared Google Drives are pirated. Authors of spiritual texts often rely on book sales to fund retreats and research. Downloading a stolen copy of a book by Osho or Mantak Chia denies them that livelihood. If the book is currently in print, the free PDF is likely illegal. buku tantra pdf
If you are searching for the free PDF simply because you are curious about sex, stop. You will be disappointed. The "sex" in Tantra is a metaphor for the union of opposites (Shiva/Shakti). Without the meditation practice, the physical techniques are just gymnastics. The internet is a cesspool of "copy-paste Gurus