For one System
You can set the Staff Size as a percentage of normal size.
1. Open Staff Settings for the Staff you are interested in.
2. Click the “Staff Options...” button.
The values range from 25% up to 250% of normal size.
For all Systems in a Layout
1. Open the Layout Settings dialog.
The values range from 25% up to 250% of normal size.
3. Close the dialog.
All Staves will now get the desired size. Staves that have individual size settings (as described above) will still be proportionally smaller/larger.
This setting is part of the Layout and can for example be used when printing a full score slightly smaller than the parts for each instrument.