Hi Joseph,
If you want to take advantage of full collaboration of items back and forth I would suggest you use the IDX format, which is used for PADS MCAD Collaborator and PTC Creo ECAD MCAD Collaboration plug-in. This is to replace the IDF format which was developed in 1992 and was stopped being developed in 1998, therefore is an obsolete format. It contains a full data dump that typically happens at the very end or very beginning of your design flow, which will result in more re-work to match the other domains database requirements.
This process for tranfering information between ECAD and MCAD with IDX is very simple.With the IDX format you synchronize your PADS and Creo interface and then send incremental proposal files to collaborate and send information back and forth. This allows both domains be synchronized throughout the full design process. When the electrical engineer exports a change you open the collaboration file in the Validate Dialog in Creo. This will allow you to immediately validate what exactly has been changed and you can accept/reject the items, which will automatically be updated in your current assembly.
If you need any additional information, please let me know.
Alex