One of the most common questions I get while doing support for SolidWorks is; "Is SolidWorks backwards compatible?". Time and time again I've had to give the unfortunate answer that, like any 3D CAD modeling program, SolidWorks is not backwards compatible. The ability to open or save a future version file back into an older format is a feature that has been requested for years. Due to the complexity of the code used to write 3D CAD software, it's not a feasible option to allow saving back to an older version. With the recent release of SolidWorks 2013 however, SolidWorks has taken steps to address this request. Starting with SolidWorks 2012 service pack 5, users will now be able to open SolidWorks 2013 files in service pack 5 of SolidWorks 2012. Users will still not have the ability to edit the 2013 file in the 2012 version, they will however be able to insert the 2013 file into a 2012 assembly. Subsequently, any changes made to the file in 2013 will then propogate in the 2012 assembly.
Here is a quick example showing what i'm talking about...
Open a 2013 part in 2012 service pack 5
Insert that file into a SolidWorks 2012 assembly
The above changes are now reflected in the 2012 assembly that this part is in.
While this feature doesn't give full functionality, it will help make the transition to the new release of SolidWorks go smoother and allow a little interoperability between vendors that are still on the previous SolidWorks release.
If you're interested in the details of everything ths new functionality has to offer check out this link...