Adobe Acrobat 7 Professional - Manual (Page 570)

Scheduling index updates
You can schedule when and how often to automatically build, rebuild, update, and purge
an index by using the Catalog feature and a Catalog batch PDX (.bpdx) file. A .bpdx file
is a text file that contains a list of platform-dependent catalog index file paths and flags.
You use a scheduling application, such as Windows Scheduler or Scheduler for Mac OS,
to display the .bpdx file in Acrobat. Acrobat then re-creates the index according to the
flags in the .bpdx file.
For more detailed information on scheduling indexing, search from the Support page on
the Adobe website at www.adobe.com/support/main.html.