Normally all I use is
[VB]
Process.Start("Acrobat.exe", strFilePath)
[/VB]
Where strFilePath is the location of the pdf file. I.E. C:\temp\document.pdf
Instead of seeing if Adobe Acrobat exists just place the Process.Start statement within a Try - Catch - Finally.
I.E.
[VB]
Try
Process.Start("Acrobat.exe", strFilePath)
Catch ex As Exception
Display a message that Acrobat isnt installed or something else.
End Try
[/VB]