David,
I think what Grenville is calling stacking is simply combining PDFs together. Some 3rd party Acrobat programs will let you combine them. Adobe, which is what you are probably referring to since you paid for it, created Acrobat, and given its cost and the fact that it is Adobe, it can do most anything. For instance, we have Adobe on every client. I can take five or ten or 100 PDFs, lasso them, right click on them, and choose to combine them. There are many options with Adobe. You can, of course, use the program to drag files out of the program or do it in other ways.
