Not finding all softwares in the Software centre

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http://askubuntu.com – I just installed Ubuntu 12.04 LTS and I am not able to find Adobe reader or Gnu plot in the software centre. When I tru to get all updates, the process goes through till about 95% and then doesnt proceed. Hence, I had to stop it there. Can someone please help me in installing these softwares. And also let me know why I am unable to view these on the software centre screen. (HowTos)