Installation log files are used to troubleshoot problems installing the products or product updates. Everything that is done before clicking the Install button is recorded in PDApp.log. Everything after clicking Install is recorded in the main installation log file.
PDApp.log: This log contains all of the actions made before clicking the Install button.
<Product name>.<Version number>.<Date>.log.gz (example: Adobe Photoshop CS6 Support 13.0.2 12-12-2012.log.gz): This log records everything after clicking the Install button and is considered the main installation log file. The product and version being installed determines the filename.