The GetPDF() method is a way to get the PDF file used for printing the letter or postcard as a binary file.
|Username||String||As provided during registration|
|Password||String||As provided during registration|
|ID||int||Matches the ID provided as the response to the original Web Service request.|
|ResultCode||int||ResultCode for the GetPDF request. See list of Web Service Result Codes|
|FileData||base64Binary||PDF document represented as binary data|