how to enable the compression on IIS7

OK, the static compression is already enabled by default. But when you need to compress the Document Manager pages, you need the dynamic compression.

So, you may proceed as follows:

install the Dynamic compression feature for your IIS role (I am speaking about Windows 2008, so…)

type the command

%systemroot%\System32\inetsrv\appcmd set config -section:urlCompression /doDynamic
Compression:true

and then, if you do not like 7 (default) as compression level, you can change it with

%windir%\system32\inetsrv\appcmd.exe set config -section:httpCompression -[name='gzip'].dynamicCompressionLevel:<value>

%windir%\system32\inetsrv\appcmd.exe set config -section:httpCompression -[name='gzip'].staticCompressionLevel:<value>

as a reference:

IIS.NET blog

IIS.NET forum thread