"Starting with SolidWorks 2012, you can open a file from a later version in Service Pack 5 of the previous version. For example, you will be able to open SolidWorks 2014 files in SolidWorks 2013. Interoperability is only supported for consecutive releases. For example, you cannot open a SolidWorks 2014 file in SolidWorks 2012 Service Pack 5."
But it depends, which version do you have? Basically, if they are in 2012 SP5, they can open files created in 2013.
In fact, solidworks of a lower version will just be able to open the file (of a future version) but we won't be able to do anything with it, it's a solid "dead". You can't save it in the lower version, let alone get the build tree back. It's just visual.
@ Stefbeno it's to be tested but I think there will be some losses and I have the impression that you will have dead volumes
Why not record in Parasolid
or go through OnShape which is able according to what I understand to recognize the functions of different SW versions so your file you send it to onshape
and take over this onshape file by your client when opening on SW
In theory you shouldn't lose anything
Give it a try and tell us
Importing and exporting files
You can import and export many types of files, not just CAD files. When importing CAD files, Onshape automatically writes back to Onshape's internal format. When exporting files, you can export to another CAD format, as well as simply upload non-CAD files. See the links below.
Import - Uploads any type of file into Onshape, either as its own document, or into an existing document. If the file is a CAD file, it will be automatically converted to Onshape format.
Download - Copy any file that has been imported into Onshape back to Onshape in its current file format on your local machine.
Export - Write an Onshape studio part or individual part to another CAD format, or a sketch or flat face in DWG/DXF format and download it to your local computer.
For any tab that represents a part or assembly, Onshape automatically writes to a supported format of your choice when you initiate an export. Onshape can write parts Studios, assemblies, and tabs containing other imported CAD files.