This is caused by a couple of the default Acrobat Reader print settings.
To print the PDF, open the PDF of your script in Acrobat Reader. Go to File > Print and a standard Windows print dialogue box will open. In the Page Handling section change Page Scaling to "None" and uncheck the two preferences below it. PDFs will then print exactly as they would in Final Draft.
NOTE: All support for Final Draft 7, including software activation, has been discontinued. You may find solutions to problems in the online knowledge base or in the PDF manual found on the installation CD.