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:
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My solution was to install wine1.5 and install Foxit Reader 5 for Windows (not the version they have for linux which is outdated).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:
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.
If all else fails, try opening your PDF in another program! I'm using Mendeley because it allows highlighting and notes. Seems to work with any PDF, no matter what the properties of the PDF are or what operating system(s) you're using.