Hi,
You know I have to thank you for the solution as by asking your question you provided me with a way to solve my problem .....
As double clicking a pdf file when the application is open with no open document works as I want it to (i.e. showing the new document in the existing acrobat window), so I decided to try out a plain vanilla shell instruction in vba instead of the AVDOC.Open statement ... and ....although not very programmatically aesthetic .... it works.
rgds