It is the same way in 2010 with plotting to pdf.  Now if you use the EXPORTPDF, it will do what you're looking for .pdf.  AFAIK this has always been the functionality of plotting to pdf, and I'll see if I can explain why this may be.  There are many industries that have many layouts in the same file.  AutoDesk put this naming scheme ( .pdf) in place for those who plot multiple layouts to pdf from the same file.  If they hadn't, then you can see what a mess it would have made.  Plotting 3 layouts to pdf would have resulted in only 1 pdf.  HTH

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