How to change PDF document dimensions - Acrobat Pro 9

Thanks for coming back to me on this guys. I'm not sure either suggestion would quite work for this problem as I wanted the whole document to reduce size. However, I've since managed to adapt the original Illustrator file and have fixed the problem

However I will certainly make note of your tips as I'm sure they'll be handy in the future

thanks again!

You should be able to use Document->Crop Pages.

Using the Margin-settings you should be able to adjust to the specific size you need.

You might play with the Touchup Object tool off the Advanced Editing toolbar.
Use the tool to select the image. Any of the four corners can be "grabbed" and a mouse drag will let you change the space occupied, on the PDF page, by the image. Not a "fine control" but, sometimes, all that's needed.

Or, in Preferences > Touchup category - the associated configuration pane permits selection of an installed image editor.
Now, using the Touchup Object tool's context menu, you can use the "Edit Image..." selection.
Edit the image and return it to the PDF.

Be well...

Not necessarily the best way to deal with the problem, but a simple way, is to print to a new PDF with the desired paper size selected and select shrink to fit page.