I'm quite familiar with Sandra Lines statement. You'll not that nowhere in it does she agree that it is a forgery. All she says is what she would say about any scan or image, even of a perfectly authentic document.
A document examiner will not authenticate an image. That's all she says.
Perhaps you missed this:
2. I have reviewed the attached affidavit posted on the internet from “Ron Polarik,” [PDF] who has declined to provide his name because of a number of death threats he has received. After my review and based on my years of experience, I can state with certainty that the COLB presented on the internet by the various groups, which include the “Daily Kos,” the Obama Campaign, “Factcheck.org” and others
“cannot be relied upon as genuine.
Mr. Polarik raises issues concerning the COLB that I can affirm. Software such as Adobe Photoshop can produce complete images or alter images that appear to be genuine”; therefore, any image offered on the internet cannot be relied upon as being a copy of the authentic document.