What does it mean to have a pulmonary lung disease? Does smoking cause this disease?

Pulmonary Disease. Pulmonary disease is a broad category which has many causes and many manifestations. Lung diseases can be innate from birth or can be a result of environmental impacts. Among these environmental influences linked to climate, geography and ecology, smoking has been clearly identified as a root cause of many lung/pulmonary ailments.
Smoking is bad. You are right - smokers are hurting their lungs, and smoking is one of the causes of pulmonary disease. But there are other causes, such as genetics, environmental exposures to chemicals and smog as well as damage caused by infections. If by pulmonary lung disease you mean copd, again, smoking is bad. COPD can also be exacerbated by other things, and is often genetic in origin.