You can edit the height and width of a photo board after it has been inserted.
To edit the size of a photo board:
Select the photo board.
Right-click and select Properties, or select Edit > Modify Elements > Properties.
Edit the Height or Width in the Properties area. If Maintain Aspect Ratio is checked, the height will automatically change if you edit the width, and vice versa. This ensures the image doesn’t get distorted.
Click OK.