The file extension BPDX is used by the Adobe Acrobat document creation software for the batch files of catalog index files (extension pdx). Bpdx files are text files that list the index files to be updated. In addition, you can specify whether the pdx file should be deleted, created or recreated.
Using a task scheduler (eg Windows Scheduler), you can call Acrobat with this BPDX file (pass it as an argument) to have the corresponding index tasks done on a regular basis. To be able to process BPDX files, you have to allow the default settings under 'Catalog-> Catalog Batch File Execution (.Bpdx)'.