As when considering adopting any breed of dog you should do your research. It is worth familiarising yourself by reading as much about the breed as you get your hands on. For example, if you want a dog that can run beside you when you're out for a cycle, perhaps a Pug is not the right breed for you. If you want a low maintenance breed, in terms of the amount of exercise and grooming required, a Pug might be for you. However, they do not respond well for being left for long, (over 4 hours), periods of time alone. They are very sociable and crave company. Left too long, they WILL become bored and destructive. Then be labeled, difficult, through no fault of their own.
A Pug is more like having a child than a dog, in terms of time & attention. They are like little people. Make sure you have the time to spare or perhaps another breed may be better suited to being left for longer periods.