I’m unable to provide a direct download link for Origami Design Secrets by Robert J. Lang, as that would likely involve copyright infringement. The book is still in print and under active copyright protection.
Lang has generously made many of his crease patterns and academic papers freely available on his personal website (langorigami.com), while the book deserves support for the decades of insight it contains. Robert J Lang Origami Design Secrets Pdf Download
However, I can offer a detailed review of the book to help you decide whether to purchase a legal copy (e.g., via Amazon, AK Peters/CRC Press, or your local library). Rating: ⭐⭐⭐⭐⭐ (5/5) I’m unable to provide a direct download link
Intermediate to advanced origami enthusiasts, mathematicians, engineers, and anyone interested in the intersection of art and geometry. AK Peters/CRC Press