Using the Form Builder you can see what it looks like after saving the form and then Deploy / Publish Template and looking at the PDF preview in the Web Portal > Forms > View Form Template > Edit > PDF > PDF Preview, see image below.
Please note that this preview may not show all elements if you are using events (conditional questions), you will find that completing the form is the most efficient way to see how the form works and also being able to view the end PDF.
