Pärnu's old city is pretty small and navigateable by foot, but it's full of small boutiques. Lots of them are on Rüütli street.
Bus connection covers the whole city. There are 26 routes and their schedules can be found at Pärnu ATP-s website.
Pärnu has a big beach that opens to the south and has lovely, almost white sand. The Baltic seaside resort.
Weather at the beach can be wet and raw even in summer, so many Estonian holiday makers go indoors to the Vee Park, which is an indoor water park at the largest beachside hotel. As water parks go, this one is fantastic, and insures that your few days at the beach won't be wasted because of inclement weather. There are lot of interesting historical buildings in the city center. You may ask special broucher and discover all of them by Your own Discover Pärnu by Your own
Just south of downtown is a modern art museum and art school. Exhibits change frequently, and are often edgy and provocative.
In winter time, consider one of the many spa hotels:
A'la carte restaurant Café Grand in the citycenter of Pärnu