The PDF form is fillable online. That means you can complete it on the web, then save it (using file "save as" in your menu bar), and email it from your email program to firstname.lastname@example.org.
Alternately, you can complete the form online and save it (using the same file "save as") and then print it out from your computer. You can scan and email it, or you can mail it.
Lastly, if you prefer to complete the PDF form by hand, use the file "save as" from your menu bar, print it out from your computer, complete the handwritten form, and mail it.