PDM Standard is only available through SolidWorks Professional and Premium. Users with only SolidWorks Standard will have no access to the PDM Standard vault in your setup.
PDM Standard entitles you to one license per SolidWorks Professional or Premium license. This license would be inserted into your existing floating network setup alongside all the licenses you have there now. It would also act independently of the SolidWorks Professional license. However, like Steve Ostrovsky said, you only have a single license of SolidWorks Professional so you will only have enough licenses to have a single user in the vault at any time. That's not going to be very effective in a vault environment if you want everyone regularly interacting with it.
SW PDM uses log in/out that is separate from the SolidWorks license. When someone logs into the vault they pull a PDM license. So, they would hold onto that license until they log out. You could minimize this by setting a timeout period in the license server options file to 20 minutes or something. The problem with only having one license is that anytime 2 people were actively working on a project in the vault they would have conflicting license needs.
Like workgroup PDm, it comes with SW pro and pre (no extra cost)
For SW standard version, you have to pay to use the PDM standard (contact your VAR for info)
We did not go with PDM at my company.
In the beginning we had 6 seats of SWX standard.
Later we upgraded 2 seats to Pro. so we could use Workgroup PDM on those - but the others could not access it.
Also, we wanted other office people to be able to access the data to send to the Machine shop, store and control documents, etc.
We would have had to get individual licenses for those seats as well as the office people.
It was just not realistic.
On top of that, we had to maintain subscription to the PDM or we would loose access. Not acceptable for us.
If we had done that and then with the recent downturn is business, we would have had to layoff an employee to cover the cost, just to keep access to our files.
You need to fully investigate everything you need from the PDM, how many users, What type of user (full access or view only), the total cost, what if you drop your subscription....
It may work fine for you but for us and the size of our company is was just not a fit.
In a bigger company I think PDM is a must.
It is for a small company also - but we have to do Manual PDM due to cost.