Below is a link to Adobe's support article on how to electronically sign PDF's from within Adobe Reader. 

https://helpx.adobe.com/reader/using/sign-pdfs.html 

Adobe Reader is installed by default on all district computers. If you cannot locate this program click on the Start button in the bottom left-hand corner and type "Adobe Reader". You should see the program listed as an available option.

Note: If you are unable to find the e-sign option on the top bar of a document there is also a pop-out window on the right-hand side (see below).