Are you so concerned about the PDF exploit on all versions of iDevices that you’re considering squandering your Jailbreak to upgrade iOS 4.0.2?  Concern yourself no more you can have your cake and eat it too.  Saurik had just released a PDF patch on Cydia that will fix the exploit and leave your jailbreak intact.

Now if only Apple would take the hint an push updates, not the entire OS every time there is a minor fix.