Assuming I understand you correctly what you want to do is done via the HTTP mod_deflate extension in Apache, you can either modify the site's .htaccess file or add the configuration to Apache's configuration file. For .htaccess you can try this:
<ifModule mod_gzip.c>
mod_gzip_on Yes
mod_gzip_dechunk Yes
mod_gzip_item_include file .(html?|txt|css|js|php|pl"py)$
mod_gzip_item_include handler ^cgi-script$
mod_gzip_item_include mime ^text/.*
mod_gzip_item_include mime ^application/x-javascript.*
mod_gzip_item_exclude mime ^image/.*
mod_gzip_item_exclude rspheader ^Content-Encoding:.*gzip.*
</ifModule>
If this fails to work remove it and replace it with this:
AddOutputFilterByType DEFLATE text/html
Adding a new line with the applicable mime type for each content type you want to compress.
