You might need to give more explanation of what you're trying to do, and why.
Probably you want to create a custom stylesheet and change the linespacing for different format markers (\p and maybe others).
You can read about creating the stylesheet by searching the PT help for the article titled "How do I implement a custom stylesheet for my project?"
You can then read the article titled "What styles can be specified in a stylesheet?" In particular, you're probably going to want to set \LineSpacing = 2 (or some number larger than 1). One thing to note when experimenting with different styles is that you'll probably have to turn PT off, edit the custom.sty file, and then turn PT back on.