As with diabetes, nobody should ever become hypertensive on a primal diet (save for rare genetic conditions, etc.). It's a clear disease of civilization as well.
If you are already hypertensive, the effects of pb are likely analogous to those in a diabetic - it will certainly help, and may indeed be curative, depending on the initial severity. If diabetes is so bad that the pancreas is burned out, then you'll likely still need some form of treatment even with pb. Likewise, if you've lost a ton of elasticity in the resistance vessels, then pb may not be curative for hypertension either.
Surely, though, losing weight and cutting out processed foods along will have a huge beneficial impact on blood pressure.
As far as tweaks, taking a look at sodium intake would be one (salt won't cause hypertension, but will aggravate it once its present). However, most folks switching to pb will see a big drop in sodium intake since it's added to so many processed foods... And following some sort of exercise regimen is also big, but probably a given for someone following pb.