Digital signatures in Adobe PDF

Using Acrobat Reader:

Sign a document (Reader 10.1.3)

In Reader 10.1.3, you can type your name, draw your signature, or place an image of your signature on a document. You can also add text, such as your name, company, title, or the date. When your document is complete, the signature becomes part of the PDF.

1. Open the PDF you want to sign.
2. Click the Sign icon in the toolbar to open the Sign pane.
   

   If the Sign icon is not in the toolbar, right-click the toolbar, and choose File > Add Text or Signature.
3. To add text, such as your name, company, or title, click Add Text in the I Need To Sign panel. Click in the document where you want to add the text, and type.
   
   

   Add Text option lets you add your name, company, or date to the PDF.
4. In the Sign pane, click Place Signature.
   

http://help.adobe.com/en_US/reader/using/WS82af097c4236e2eb3543853d130e391c674-8000.html