How can we make certain fields of a word document Uneditable? How to change a word document to editable PDF?

I have a word document which I want to create like a form( some fields editable and some noneditable). Is it possible in word?

Can I use PDF ? How it works ?( I want editable and non editable fields)How can we make certain fields of a word document Uneditable? How to change a word document to editable PDF?
Have a try Simpo PDF Creator.

http://www.softpedia.com/get/Office-tools/PDF/Simpo-PDF-Creator.shtml