Depends on the *.pmf author. In ArcMap and using the Publisher toolbar to create the *.pmf, the author can create a data package in a separate location from the original data. For the data format in the Data Packaging wizard, the *.pmf author can select File Geodatabase, Compressed File Geodatabase, Compressed and Locked Geodatabase, or Copy data in existing format. If the *.pmf author selects File Geodatabase for the data package for the *.pmf, then a user with ArcMap could edit that data (but could edit the data using ArcReader).
Hope this helps.
Regards,
Robert LeClair
Esri-Denver