Can a PDF form created on jotform be digitally signed?

Hello ciafairborn,

Unfortunately no. Please be noted that signature widget or any other widgets requires extra scripting that are loaded from external resources and currently does not work in PDF form.

You may like to take a look at the following guide for more information on the limitations of PDF forms:  http://www.jotform.com/help/312-Fillable-PDF-Everything-you-need-to-know-about-JotForm-Fillable-PDF-Creator 

Thank you!