How much has it changed?
When open in different applications, the size may dispaly a little bit different due to the rounding-off reasons.
Please also make sure the size are displayed in the same measurement unit.

Also verify the page settings when save to PDF.
Save & Send > Create PDF/XPS Document > Create PDF/XPS > Options > Printer Options

BTW, when print to XPS, will the it change the size?
Max Meng
TechNet Community Support
