The edits were not done with photoshop, they were done with Mac OS X 10.6.7 Quartz PDFContext. It's in the header.
And yes, actually, there were edits to the document text. I'm being completely serious, and you can verify this yourself. I don't have Quartz, but I have Illustrator, and if you do Windows->Actions->Links, you can see what sections of text were edited. That doesn't tell you what it was like before the edit, and in fact it doesn't even tell you that the edit changed any content. I would guess that the edits were simply to make the document more legible. But it has been edited.