If you're planning to print a score, you should choose the download file that matches your printer paper size.
By choosing the correct file, there should be no need to resize the output prior to printing.
Just incase you're not sure which format to choose, here are some guidelines:
Letter applies to North and South America. The paper dimensions are - Millimeters: 215.9 wide x 279.4 high; Inches: 8.5 wide x 11 high.
A4 applies internationally and is used in most other areas of the world. The paper dimensions are - Millimeters: 210 wide x 297 high; Inches: 8.27 wide x 11.69 high.