LiveCycle Forms ES accepts form designs in either of the following formats:
XDP is the file format created by LiveCycle Designer ES. Choose this format to submit the form design, any form data, annotations, accessibility tags, and all other relevant information needed for LiveCycle Forms ES to subsequently render the form at run time. You must choose this format if the form will initiate server-side processing.
Choose PDF if the form contains a signature field or if users will be expected to save data directly in the PDF form at run time. If the rendered form will have a fixed layout and you expect the form to be requested often, providing the form design to LiveCycle Forms ES in PDF can improve LiveCycle Forms ES run time performance.
If LiveCycle Forms ES will be used to render HTML forms or forms that have a flexible layout.
See also 

Saving a form design: XDP or PDF?