At first you need to download latest Adobe Acrobat Reader DC.
- Open the document with Acrobat Reader DC.
- Select the Tools tab --> Fill & Sign
- In the next window click on open under the heading Compile and Signature.
- Select top of the document sign command
- Select the + next to the item Add signature.
- Now you can choose from three ways to sign this PDF:
- Type: write your name and surname and will be shown.
- Draw: mouse or a touch screen you can make your signature as if I had a pen and will be saved.
- Image: Upload an image of your signature from your PC.
- Click on the apply button and drag the text box where you have to put signature and you have finished.
Here is official Adobe procedure: