1. Open the scanned PDF file with Adobe Acrobat XI Professional Edition.

2. Click Tools → Content Editing → Add a picture and add an electronic signature.

3. The insertion is complete, as shown below:

4. Adjust the size of our electronic signature picture.

5. After selection, there are eight grips for editing. After adjustment, move them to the location where you want to sign.

6. The signature has been added. Click Save to finish.