Various embodiments of the present disclosure provide a pneumatic inflator for automatically inflating inflatable articles, such as dunnage bags, to a desired pressure. Generally, once activated, the pneumatic inflator of the present disclosure inflates an inflatable article via a compressed air source until the air pressure inside the inflatable article reaches an operator-selected desired pressure. Thereafter, the pneumatic inflator automatically stops inflating the inflatable article. In various embodiments, the pneumatic inflator also includes a manual shut-off that, when activated while the pneumatic inflator is inflating the inflatable article, causes the pneumatic inflator to stop inflating the inflatable article. The pneumatic inflator of the present disclosure thus enables automatic inflation of inflatable articles to particular, operated-selected desired pressures with limited operator input.