Mike O'Flaherty, a designer and CAD administrator, gives us a little hint about customizing AutoCAD's PGP file.
"Creating or modifying a command alias by editing the ACAD.PGP file is quick and easy, whether you access it via the pull-down menu (Tools > Customize > Edit Program Parameters) or the ribbon (Manage > Edit Aliases). After making changes, many people shut down AutoCAD and restart it to make the changes available. There is no need to do so, however; instead, run Reinit at the Command line, and in the dialog box that appears, check PGP File and click on OK. Your new aliases are ready to use.
"As a further suggestion, always add your custom aliases to the end of the file; don't try to insert them alphabetically. When you upgrade AutoCAD to the next version it's easier to copy your custom aliases to the new file if they aren't scattered among the default aliases. Also, aliases are loaded in order, and placing your custom alias at the end ensures that it will supersede any stock alias using the same shortcut."
Notes from Cadalyst Tip Patrol: Editing the PGP file in AutoCAD is one of the easiest customizations that a user can do. It's also one of the easiest to take with you. AutoCAD loads the PGP file when it loads, so any changes to it won't come into play until it is reloaded. There are two ways to do that: reload AutoCAD (turn it off, then back on), or follow this tip and use the Reinit command.