How did I miss this for so long? I finally found the easiest and free way to sign pdf contract on mac with Preview. It will only require a webcam.

These are the steps:

1. Open your document with Preview.
2. Go to Tools > Annotate > Signature
3. Click on “Create Signature from FaceTime camera”
4. Put in front of your camera a white paper with your signature. When you signature get recognized, accept it.
5. Click anywhere on your document to add the signature.
6. That’s it! Save your document.
7. Your signature will be registered in Preview for the next contract

Wasn’t that easy?