I have done it for Windows machines before, and usually I could just replace the preference files/registry entries right inside the.msi installer, using tools like Orca, Wise Package Studio and so on. Most applications require some tampering with their preferences before deploying. Recently I was tasked with finding out a way to prepare OS X applications for automatic distribution to multiple machines. Flat File Editor is useful for viewing large fixed-length files that have a well defined record layout. I am not aware of any Apple recommended tools to edit existing package, pkg or mpkg, files.Most packages are signed and thus any changes will invalidate their signature although resigning is simple enough using pkgbuild and an appropriate installer certificate. This document will try to document the Flat Package Format introduced by Apple in Mac OS X 10.5. Flat Package Format - The missing documentation Description. Learn more about the Mac OS X application, Flat Package Editor (.flatpackageeditor) by Apple, in the iBoostUp software database.