Layout tab > Devices group > 
Symbols menu > Symbol scale
With this function, you can you can define a symbol scale for a drawing. The inserted symbols will then be scaled according to the selected factor in X and Y direction.
The function is also available in the Symbols window.
A large part of the Layout symbols are scalable. Symbol scale factors are often set according to the printing scale.
Note: Changing this setting does not affect symbols already in the drawing.
Note: The symbol scale factors have no effect on symbols whose size is fixed or defined by the user (e.g. linear light fixtures).