Picture size when exporting to pdf

I have a graph that I want to export to a different size than its native size. The two commands

SavePICT/E=-2/I/W=(0,0,6.4,3.6)

and 

SavePICT/E=-2/I/W=(0,0,1,1)

result in identical pdf files, as far as I can tell. Is there a way to export a graph to a pdf file while scaling the graph to a different size?

Not on my system.

make/N=101 swave=sin(p)
display swave
SavePICT/E=-2/I/W=(0,0,6.4,3.6)
SavePICT/E=-2/I/W=(0,0,1,1)

Have you by chance set the graph to a fixed size? 

Have you set one of the graph size modes? What you describe sounds like you have set Absolute size mode for both width and height. That setting is found in the Modify Graph dialog.