As long as the pretzels that are expired smell okay and do not have any mold or anything on them then eating the expired pretzels is okay and you should not get sick.
Pretzels and other snack foods contain preservatives in order to maintain shelf life of the pretzels and snack foods which make them last longer.
Unopened Pretzels can last for a year or longer past the expiration date and are okay to eat for at least a year past the expiration date of the Pretzels however they may be stale and not as tasty as fresh pretzels.
Once you open the pretzels they begin going stale sooner if not sealed back up and then they may start smelling bad and have a bad taste to them.
If they smell bad and or have a bad taste to the pretzels then throw them out.
You would probably be okay but you could get a stomach ache or suffer from food poisoning which would likely go away on it's own but it's not worth the risk.