I would very much like to add my signature like I do in Preview. Others use this to have a paperless office?

To ask Apple to add a new feature, go to

http://www.apple.com/feedback

Use the Provide Pages Feedback menu item in the Pages application menu. That goes directly to the Pages product team.

Presently, Pages does not have a built-in signature feature, nor can you just copy/paste a signature out of Preview unless you take a screen shot of the signature annotation applied to a PDF, and then send that to the clipboard (⌃⇧⌘4). Next, you paste the image from the clipboard into Pages. The image will have a white background.