They do shed, but not excessively more than any other dog. Puberty is probably the major factor in how much they shed.
The fact that you saved this question for even later to ask it implies that you haven’t had a pug or pup around and lived with one for a good amount of time and then enough research to feel knowledgeable to answer this question. So we’ll go ahead and answer it based on what we see online at Google pets.
A lot of dogs may be confused about the exact definition of the word “shed” as their hair will not come out as easily as other breeds such as poodle or Irish terriers, but those breeds are meant to have less hair because those breeds needless shedding…