"Fillable" documents in PDF format require Adobe Acrobat to work properly. Most modern browsers (e.g. Firefox, Chrome, Safari, Edge) have built in PDF Viewers, but these built in viewers may not allow you to interact with a Fillable PDF Form. Please download the document and open it in any version of Adobe Acrobat for full features.

A free version of Adobe Acrobat Reader is available here: https://get.adobe.com/reader/