For image object in PDF file, please do as follows to maintain its aspect ratio when we resize it:
Go to "EDIT" menu>select "Edit object>”image" tool to single click on image object to select it, then please just drag one of the four corners re-size handles outwards or inwards to resize the image proportionally. If you drag the other re-size handles (left &right re-size handles or top & bottom re-size handles), you have to holding shift key while dragging the handle.
For Image object, do the followings:
1. In Edit menu, click Object Edit, choose Image.
2. Click on the image, drag one of the four corners to resize the image. You can also hold down SHIFT on the keyboard, and drag any size handle in a proportional way.
For image annotation object, do the followings:
1. Choose Select Annotation tool
2. Click on the image, hold down SHIFT on the keyboard, and drag any size handle to resize the image.
