PRE7 doesn't support timers and I don't recall seeing it on the PRE8 new features list.
As work-around for fairly short timers you can simulate the effect by manually creating the necessary graphics and adding them to the timeline in the appropriate position. And, although I've never tried this one myself, I don't see why you couldn't capture a timer video and add that to the timeline.
Insanity is hereditary, you get it from your children
There are two programs, both with the same name, DVDate, and one of those can do this.
PrPro has a TimeColde Effect, as does AfterEffects. The one in AE offers more options like fonts and color.
If you are attempting to edit a multi-cam shoot, PrPro has a Multi-cam function for syncing material from two cameras.