How to add a digital signature in Adobe Acrobat Reader.

On the Left Side of the PDF, there is a tool bar. 

1: Click on the Icon that looks like a ink pen. 

2: Select Add Signature. 

3: Click on Type and type out your full name.  You will see your signature created. 

4: Click on Save Signature. 

5: Click on Apply.

You will then see your mouse icon as your signature and click on the area where you want to sign. 

Please scroll down further to see the Troubleshooting tips.

Image Example: 

If you can't simply just "Save", and are forced to "Save as..", you may need to do one of the following -

1. Turn off document preview in Windows explorer, as shown highlighted here -

2. Turn off Enhanced security in Acrobat Reader DC, by opening Acrobat Reader, then clicking on the Edit menu, then selecting Preferences, then click on the "Security (Enhanced) category, then uncheck the "Enable Enhanced Security" option.