Changing the Object Size
To resize an object with the mouse, select it and drag one of the handles on its border.
In order to resize an object while preserving its aspect ratio, drag one of its corner handles. If you resize holding down the Shift key, the proportion of width to height will not be preserved.
In order to change only width or height of an object, drag a handle in the middle of the object border side. If you do this holding down the Shift key, the program will preserve the object's aspect ratio.
You can also input exact dimensions of an object in the Geometry tab of the Inspector. The measurement units can be changed in the Document tab of the Inspector.
If the Fix aspect ratio option in the Inspector is activated, the program will resize an object preserving its aspect ratio whatever method you use.
Resizing a Group of Objects
It is possible to resize groups as well as several selected objects (let's call them "a temporary group"). Resizing a group or temporary group with the mouse will affect the group bound in the same way as a single object. When the whole group or any of the objects in the group has Fix aspect ratio set, the bound of the group will preserve the aspect ratio, and all of the objects will do as well. In case when none of the objects has Fix aspect ratio activated, you can set any aspect ratio for the bound, and the same aspect ratio will be applied to all of the objects.
If you select several objects and input new width and height in the Inspector, the values will apply separately to each of the selected objects. The program will take into account objects' Fix aspect ratio options individually.
Finally, if you use the Inspector to resize a group, new width and height will apply to the bound of the group. The size of the objects will change respectively. The Fix aspect ratio option activated for any of the objects or the whole group, will preserve the aspect ratio of the group and all of the objects inside.