The first time you open Pro/Weld it appears, at first glance, that you've stumbled upon something great. Turns out, it's not very useful for a fewreasons:
The weld symbols end up with a number in the tail and it can't be changed. I'm assuming the number represents the order in which the weld was added and as far as I know this is not a standard. So for detailed drawings this doesn't work.
It's generally not a good idea to use features in assemblies (ie assembly cuts) and this is an assembly feature. It extends regeneration/refresh times and in larger assemblies this becomes an issue with PC resources. We have fairly large assemlbies here but have pretty fast PC's and it's still a problem.
The weld geometry are quilts, not solid geometry, so if you're wanting volumes for any reason it may be difficult. However, I believe you can manually assign mass properties.
You're better off assembling an empty part(s) and modeling the welds as solid protrusions in the part(s) (be careful with your references, a skeleton may be sueful) and then either using annotations in the model or drafting weld symbols in the drawing.
Hopefully someday it will be more useful.
