Notice: This article may contain information for multiple versions of Passpack, be sure and read the section appropriate to your version. How do I know what version I'm using?
Passpack v7
Not automatically, sorry.
Passpack can securely store passwords for you, it can suggest strong passwords for you, and it can even log you into websites - the one thing it can't do is automatically change your passwords for you on other websites.
Here's how to change your passwords to strong ones.
Passpack v8 (Preview)