do you mean a editable ppt with dynamic content?
Or just an editable ppt?
You can allways upload a ppt as an attachment. Edit it in ppt, save it on your HDD and the upload it to CRM again.
There is no way supported way of using CRM as a document ressource. For that I would suggest you use Sharepoint instead.
Rune Daub Senior Consultant - Dynateam CRM http://www.dynateam.dk