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Hi Nathalie,
In AutoCAD for Mac you can also use PURGE command, but it has only command line interface:
http://docs.autodesk.com/ACDMAC/2013/ENU/filesACRMac/GUID-C3876E92-3478-449C-8FAB-DA760B2EDD09.htm
Just type PURGE at the command prompt, than select which type of object you want to purge by typing one of the options name and hit Return, than if you want to purge all objects of this type, hit Return once again, than type N and hit Return again.
If you want to purge all unused objects, select ALL option after you will call PURGE command, hit Return once again, than type N and hit Return again:
Command: PURGE <-Hit Return here
Enter type of unused objects to purge [Blocks/DEtailviewstyles/Dimstyles/Groups/LAyers/LTypes/MAterials/MUltileaderstyles/Plotstyles/SHapes/textSTyles/Mlinestyles/SEctionviewstyles/Tablestyles/Visualstyles/Regapps/Zero-length geometry/Empty text objects/Orphaned data/All]: a
Enter name(s) to purge <*>: <-Hit Return here
Verify each name to be purged? [Yes/No] <Y>: N <-Type N and Hit Return here
Maxim
