Just downloaded the update via command centre. Also there was 'sonar local documentation', which appeared to be a .pdf file called Reference Guide. When I went to the location I thought the .pdf had been downloaded to, there was only the original ref guide version 21.00.00. 
What am I misunderstanding here? 

portesham
Just downloaded the update via command centre. Also there was 'sonar local documentation', which appeared to be a .pdf file called Reference Guide. When I went to the location I thought the .pdf had been downloaded to, there was only the original ref guide version 21.00.00. 
What am I misunderstanding here? 

Same here. I even ran the installer again so I could watch where it was putting the Ref Manual, but it seems to be unchanged. So I haven't yet figured out how to use Drum Replacer.
 

Haha!  Me too, ran the installer again, still can't find the file................

The help file (chm) has a section on Drum Replacer.  I haven't looked thru it all, but it is there  :)

Get there with Help > What's New
 

So, what appeared to be a new reference manual .pdf, was actually an update to the help files accessed from within Sonar?

portesham
 Also there was 'sonar local documentation', which appeared to be a .pdf file called Reference Guide. When I went to the location I thought the .pdf had been downloaded to, there was only the original ref guide version 21.00.00. 
What am I misunderstanding here?

Historically the Reference Guide was created from an early release of the chm. It never was updated. The most current version of help is the web based help here http://www.cakewalk.com/Documentation?product=SONAR&language=3&help=toc.html. The local chm gets updated with every release. This may change with the new delivery model but I don't think it has so far.

But for sure the installer writes (or maybe attempts and fails to write) a new pdf. Why do they bother to do that if its the same old same old? Actually, I much prefer to look at the pdf version, so I wish that they would keep it updated.

Hey, I'm just happy to have info about the awesome new Drum Replacer available somewhere :)

ChristopherM
But for sure the installer writes (or maybe attempts and fails to write) a new pdf. Why do they bother to do that if its the same old same old?

Because it is part of the local help package. There is only one set of installers which (in general) are cumulative.