I downloaded Adobe acrobat 9.5.1 reader software package from Adobe's site. The .deb extension. But i cannot see the comment menu under the tools, in any pdf file that i am trying to comment
That is because Adobe Reader 9 does not have commenting features :)
Adobe Reader XI has commenting and highlighting:
Can I use Reader XI to add comments and highlights to a PDF file?
Reader XI is the first version of Reader that enables users to annotate PDF documents using a full set of commenting and markup tools, including sticky notes, a freehand drawing tool, and typewriter, highlight, underline, and strikethrough tools. You can also use Reader XI to participate in shared document reviews, with team members seeing and building on each other’s comments to speed up review cycles.
Check this post for pdf commenting.
I didn't find any native Linux pdf reader capable of annotations.
My solution was to install wine1.5 and install Foxit Reader 5 for Windows (not the version they have for linux which is outdated).
Add the wine ppa:
sudo add-apt-repository ppa:ubuntu-wine/ppa
sudo apt-get update
sudo apt-get install wine1.5
Then download the Foxit reader for windows installer and run it.
If you want to have the Foxit icon instead of the wine icon in the launcher, then see this post.
Works like a charm.