PEMDAS Widget will automatically check for updates. Since PEMDAS is a Dashboard Widget, it doesn't have the capability to download and and install an update automatically, so it will simply display a notification screen if an update is available:
Enabling/Disabling Checking for Updates
If you would like to disable this functionality, uncheck the Check for Updates checkbox on the back of the widget, shown below. You can also temporarily disable updates by clicking on the "Skip Update" or "Remind Me Later" buttons when the update notification screen comes up.