best to glue it all down. I am sure there is the option of perimeter, but I would check with the manufacturer, it depends on which product in the line you decided on.

the problem with a glued down underlayment is you can never get it out,you might concider staples,one every six inchs in every direction,every three inches on the edge.(this is the recommended method by armstrong and mannington)....good luck

With the glue, I meant the sheet flooring.
What kind of staples would I use on the underlayment. Do I need an air stapler or could I use a regular staple gun?

An air stapler is the best. Staples hold really well. I know because I've had to take it up to put in a wood floor and it doesn't come up easy when it's stapled down.

Franklyn
http://woodfloorist.com/catalog.html