Sorry you are having trouble with the margins, but its an easy fix! In the print dialog box, there is an option for "Shrink to Fit Page" or "Scale to Fit" or just "Scale."
Make sure it is set NOT to scale and it prints at 100%.
Screen Shots of what you might see...
Step 1: Select Print using System Dialog
Step 2: Click the Preferences button
Step 3: Choose the Effects Tab, then make sure Resizing Options use "Actual Size."
Step 1: You may need to click "Show Details"
Step 2: Uncheck Scaling