I use Photoshop and now starting on Illustrator but I can't work out how to change the size of the overall image. I have opened a pre-existing one but unlike Photoshop I can't see where to find the existing size then to be able to enter the new required size. Example is the current file is 64cm wide and I want to go to 100cm and keep the proportions constrained
There are many possible ways
but as you already uses photoshop I'm gonna tell you little similar.
=> If you want to change size of artboard(canvas in photoshop) you can do it either via artboard tool ( shortcut is Shift+O ) or either by going to
Document setup - Edit artboard - Desired size
=> now if you want to scale image the best practice is to do same as photoshop while turning smart guides on. ( select layer and dragging transformation circle while pressing Shift to keep proportions constrained ) and if you want to scale it by absolute width like in percent then go to
Object - Transform - Scale and if you want to scale to exact value then just use the tool bar and edit the value ( below is the image )
==> image contains practice of scaling artboard via bar and scaling via both dragging and bar . sorry couldn't add other methods because of size limit of gif.
Hope it helps :)