What is "it" that does not allow you to do it anymore: Acrobat, Reader, which version? What kind of signature are you trying to add: ink-signature (stamp), e-signature (EchoSign), digital signature? What do you mean by "weird digital signature"?
I have Adobe Acrobat XI, I am trying to draw a signature. When hit, place a signature, I get a request to drag a box somewhere on the document. Then it request that I select from a certain selection. It does not state to draw or screen shot a signature.
I still do not understand what you're trying to do. Which group on the "Sign"panel you are using: "I need to Sign", "Get Others to Sign"or "Work with Certificates"? Which selection you click on? Is it "Place Signature" in "I need to Sign"?
If it is and you get a dialog to draw a rectangle, it means that you previously selected in "Place Signature" the "Use a certificate" choice. This is a digital signature of the same type as in "Work with Certificates". If this is not what you want, click on the down arrow next to the "Place Signature" (looks like a triangle) and choose "Change Saved Signature". You will get a dialog that allows you to change the signature type. Select the one that you want to use and it will be used in the future every time when you click "Place Signature" until you choose "Change Saved Signature" again.