No, PDM doesn't use the $PRP or $PRPSHEET modifiers.
The createdby and checkedinby values could be set using the <Logged In User> value on the card.
There is also a current state value.
In order for variables to get applied to a file when checked in it has to be on the card. Once a file is checked in the custom property in the file can be populated with the card data as long as the PDM variable is used to store the information.
If you change the variable value in PDM the next time you access the file it will automatically update the custom property or note on a drawing, but variables only update during check in and state changes. And only the custom properties that are directly linked to a field on the card. You cannot update a variable that is not on the card assigned to that folder.