Create a signature with an image(PNG format for example), click Signature on the toolbar, or Annotate on the main menu -> Signature, or right-click -> Annotate -> Signature. On New Signature, select Image, and add an image from a file. You can choose Remove white background from image to remove the background. After that, you can change the opacity of the image signature.
Plus, you are allowed to create the signature directly in PDF Reader Pro for Mac with your keyboard, trackpad or the mouse.