Part I
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7) 1. Overview
"takes the load of the disabled node" <-- reads like a typo for 'takes the load off'; awkward

8) 1. Overview
"Two distinct functions must be performed" <-- by...? Try "This involves two distinct operations:"

9) IMPORTANT: 1. Overview
"Sessions state replication" --> "Session state replication"
"is handled by JBoss at the application level" <-- if it's handled at the application level, it's not handled by JBoss. Perhaps this should say "on an application by application basis"? Or does JBoss delegate responsibility to the application?

10) 1. Overview
"A cost effective way of managing load-balancing is..." <-- hyphenation is wrong. cost-effective and load balancing, please

11) 1. Overview
"Apache httpd " <-- described previously as Apache httpd Server, pick one and stick with it

12) 2. Download and Install
"Apache httpd is included..." <-- described previously as Apache httpd Server, pick one and stick with it

13) 3. Configure load balancing using Apache and mod_jk
"Apache" <-- described previously as both Apache httpd Server and Apache httpd, pick one and stick with it, or say "hereafter referred to as Apache"
(Last time I will mention this unless it develops a new reference; it's running rife throughout the document.)

14) STYLE: 3. Configure load balancing using Apache and mod_jk – Prerequisites
The weighting of the Task header and the Prerequisites header is the same, which makes it look like the steps actually belong to the Prerequisites.

15) 3. Configure load balancing using Apache and mod_jk – Task: Configure Apache to Load mod_jk
"...add a single line at the end of the file." <-- you then give an example that is not a single line.

16) 3. Configure load balancing using Apache and mod_jk – Task: Configure Apache to Load mod_jk
Really don't like the Important and Notes coming before the config file in step three. I don't think you need IMPORTANT or NOTE here, just tell them that they need to provide paths for these things.
You also assume people know what a directive is.
It might be best to split this step into the various segments of the configuration file, and provide a complete example config file as an appendix. For example:
<screen># Load mod_jk module

1. Specify the filename of the mod_jk lib
   LoadModule jk_module modules/mod_jk.so</screen>
   The <literal>LoadModule</literal> directive must reference ... etc.

17) 3. Configure load balancing using Apache and mod_jk – Task: Configure Apache to Load mod_jk
"...use the JkMountFile directive to specify a mount points configuration file." --> missing apostrophe, mount point's

18) 3. Configure load balancing using Apache and mod_jk – Task: Configure Apache to Load mod_jk
"Specify the URL to forward..." --> Specify the URL whose requests should be forwarded... ?
"...and the worker name" --> and the name of the worker node you want to handle those requests ?

19) 3.1. Configure Worker Nodes in mod_jk
round robin --> round-robin?

20) 3.1. Configure Worker Nodes in mod_jk
"Append the following information into" --> append to, not into

21) 3.2 Configuring JBoss to work with mod_jk
jvmRoute isn't marked up at all

22) 3.2 Configuring JBoss to work with mod_jk
Note refers to community content.
Additionally, the URL displayed in the document is not the URL that the link resolves to.