I don't know if this "problem" is by design but it is causing great issues in collaboration.
I work with pople that have AutoCAD versions 2010, 2011, and 2012. We agreed that all our collaboration dwgs would be version 2010. When I change annotation scale in my drawing (having ANNOAUTOSCALE turned on) to update annotative objects to current scale, AutoCAD does this to xref drawings also, but aditionally upgrades xref dwg file version to 2013. My colleagues then can't open their own dwg files since they are upgraded to 2013 version.
Problem:
AutoCAD 2014 upgrading externally referenced drawing file version when automatically adding annotation scale to objects in main drawing.
When ANNOAUTOSCALE is turned on, AutoCAD automatically adds annotation scales for existing annotative objects, including annotative objects in xrefs. This means that AutoCAD must modify externally referenced drawings to add annotation scales to annotative objects. AutoCAD then modifies external DWG to latest supported version - 2013.
Is there an option to set AutoCAD to leave current version of externally referenced DWGs?