There are a few ways to convert a4 to a3 in Photoshop. The first way is to use the “copy” command. This will create a copy of the image, and then you can use the “paste” command to paste it into the “image” field of an “edit” panel. The second way is to use the “select all” command and then use the “copy/paste” command to paste it into the “image” field of an “edit” panel. The third way is to use the “select all, copy/paste”, and then use the “CTRL+C” key to copy it.
