By default, the views in a dashboard automatically scale to fill the entire window. This means that the size of the dashboard can vary from machine to machine, depending on the screen resolution and the size of the window. While sometimes you want the dashboard to automatically scale to fill the window, you can ensure a consistent layout by specifying a fixed size for the dashboard. The size of the dashboard is displayed at the bottom of the Dashboard window.
Please look into following documents:
I've had similar issues. I'm going to assume you are talking about a published dashboard and the user is trying to turn it into a PDF. If viewing and printing works correctly on one machine, but results in XXXX or some strange margin-fail on another...try deleting the temporary internet files on the offending machine. This worked for me.