Depending on the word application you use (e.g. Microsoft Word 2016), it's on the Picture Tab. If you click on the Format window, a new set of options will appear on the ribbon. Beside the picture styles option, there is the size option where you could adjust the size of your image pasted in the word document. If you wish to crop the picture, there is the crop thumbnail in the size option. You could crop the picture free-form or by dimension.