Is there any app for electronic signature solution? Is there any app for signing the documents (PDFs) by electronic signature?

Similar to on-line solutions such as HelloSign, EchoSign, XolidoSign, eSignly, DocuSign, Signsquid, RightSignature, PDFFiller or free Fill and Sign PDF Forms (Android app), but as an application for OSX.
Preview can sign documents, since v5, currently at v7 - 
Sign a PDF document