It depends on the material and what you want the look to be. A few years ago I had my mom size down a linen dress that i had bought...1: because it was exactly what I wanted...and 2: because it was on sale at an incredible price......
BUT ...the darn thing was 6 sizes to big lol lol
: .
She put 2 darts in back, shortened the straps and moved the buttons all within about 20 minutes.
So yes it can be done just be careful and know what you want and your measurements beforehand.