You will need to select your image in Edit Mode to make it the active document element.
You will know it is the active document element because of the red border surrounding the image. You will see the options for Clip and Crop. They will only be accessible if your image has been selected.
You can also right-click an image while the Edit mode is active and choose the Clip/Crop option from the context menu.
How to use the Clip Feature
Select the Clip Option. The icon for the mouse will change into a cross. Hold down the left mouse and drag the cursor to highlight the area of the image you would like to keep.
When you release the mouse button, you will see a preview of the final result.
You can reposition the area you would like to keep. Hold your mouse button down over the selected and move the cursor to change the position. Using the circles on the border of the selected area you can change the size.
To rotate a clip, hover your cursor over the circle handle and when a rotation arrow appears, click and drag it until the clip acquires the position you want.
Click on Apply Clip to finish the action.
Click Cancel to cancel the clipping.
You can select the image again and click on Edit Clip to reposition the clipped area at any time. PDFsam Enhanced will remember what the original image looks like.
How to use the Crop Feature
Choose the Crop Option. The border around the image will turn black.
Drag the corner of the box. When only the part of the image you wish to keep is visible, release the mouse button:
When you release the mouse button, you will see a preview of the final result. You can reposition or resize the cropped area. Once you are finished click on Apply Crop to continue. The selected area will be all that remains.
If you don't have PDFsam Enhanced yet, you can purchase it here.