Hi Paul,
I don't think you can open a copy. Acrobat opens the file that the user has selected.
However you could script so that the user is prompted to save the form if the file name matches the template. Say the form is named "My Template.pdf". The following script in the docReady event of the form1 node should work:
if (event.target.documentFileName == "My Template.pdf")
{
app.execMenuItem("SaveAs");
}
This means that when the user renames it, they will not be prompted to save as again.
Hope that helps,
Niall
PS: This won't work in LC Designer Preview, as the file name when previewed is generic, for example "c4BN23ms78.pdf". You would need to open the form in Acrobat/Reader.