If you are using a PDF for quick reference, consider buying the physical "P.L. Ballaney" paperback. It remains one of the best books to have on your shelf for open-book exams and long-term professional reference. Final Verdict
A classic textbook for Mechanical Engineering students. Great for understanding mechanisms, velocity analysis, and vibrations. Includes tons of solved problems for exam practice. theory of machines and mechanisms by pl ballaney pdf link