Signature not active in Adobe LC Designer ES4

Hello,

I've created some forms using Adobe Livecycle Designer ES4. I've added a signature fields, which is not working not even in the preview mode and of course also not is Acrobat Reader. If I check the properties of the document it looks like the signing is not allowed. How can I change the setting?

Image may be NSFW.
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Image may be NSFW.
Clik here to view.

Thanks in advance!