What's the Point?
If you check the box for "Print Editable PDF" on the FINALIZE page, you will be able to edit information in the fields of a form after the form has been printed to PDF. The Print Editable PDF checkbox will remain checked after you have clicked on the checkbox.
If this box is not checked, when you click the Print button in the Quik! Form Viewer, the resulting PDF will be locked down, and all fields will be un-editable (a.k.a, "read-only").