BP Forms relies on the CUPS-PDF driver on the Linux Print server to produce PDF documents.  CUPS-PDF is a special print driver.  By creating CUPS printer on the print server that uses the CUPS-PDF driver, CUPS will deliver the document as a PDF stored in a directory rather than to a physical paper printer.  This PDF can then be accessed by your program or by your user's as needed.  The name of the PDF file will be the name of your generated .odt file with the .odt replaced with .pdf. 

Most BP Forms systems are configured to drop the rendered pdf documents into a subdirectory under the BPIFORMS account directory. 

For example: 

.../BPIFORMS/bpi_forms/pdf

A more comprehensive discussion of PDF configuration can be found in Managing Printers and Jobs