Are you sure it pasted as test? Many pdf's are images, and you cannot copy/paste the text.
Does photoshop show it as a text layer? If so, you should have no difficulty editing it.
Post a screen shot of the layers in photoshop if this still doesn't make sense.
I think that the Copy/Paste operation brought the text from the PDF in as an Image, and NOT as a Text Layer, which would be editable.
Same post to the PS forum.
See the replies on the PS forum.