Hi GAD41,
With the PDF document that you are trying to print being a fixed format, you do only have a couple of option for changing the margins/size.
1. In the print screen you may have an option for fit to page
2. Also in the print screen should be an option for scale to fit, you may have to try this one a couple of times to get the right settings.
3. Using a PDF editor which is hard to find a free good one. Usually needs to be purchased.
Regards. :)