OpenInWindowEx keeps Acrobat in Memory (VB.Net)

If I use OpenInWindowEx without creating an AcroDoc instance (directly an AvDoc in a Panel) a full Acro-process starts (Acrobat.exe in the Task Manager).
Once finished, closing the app, the Acrobat process keeps running, rerunning the app creates a process double the size (2 processes?)
With (2?) process in memory the OpenInWindowEx doesn't do anything.
Should I create a non-visible Acrobat-instance, which I should stop everytime?
It seems like an "anonymous" instance gets created.

Figured it out!!! The Avdoc is now global, and tested "is Nothing", if not then AvDoc.Close(1). I can now update the panel with another doc. Acrobat does stay in memory, meaning that I can probably not use without stopping that process.....

the process can be examined: If Process.GetProcessesByName("Acrobat").Lenght = 0 Then messagebox.show("Acrobat isn't running")