At page 64 of the solidWorks 2011 what's new, they talk about File Synchronization.
I can't see this View > Show Warning Watermark command.
I use W7 64-bit and SW 2011 SP2 64-bit en Italian language.
I attach an assembly out-of-date and the relative part.
You need to open the assembly with eDrawings and try.
I don't see any watermark.