Unable to sign pdf document on Mac

Hi,

I am unable to sign pdf document on Mac. I have installed Acrobat reader and its up-to-date. My DSC is available in Keychain Access.

When I select to digital sign the documents, its prompting me to select the area where I would like the signature to appear. And upon selecting the area, it says signature field requires a digital signature identify and if I would like to configure one(Is this expected?). And when I say configure digital id, it gives me 3 options.

1) Use a signature creation device

2) Use digital id from a file

3) Create a new digital id

What am I missing? And how should I proceed on this?

Thanks,

Rajasekhar.