open a pdf-file at a certain page from within HTML

Might be the manual of evince the default pdf document reader of Ubuntu migth help you...

Open a Terminal from the menu Applications → Accessories → Terminal and type:

man evince

Hope this helps

Then try also to install Acrobat reader in Ubuntu... but try also to install Opera browser and try with that...

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Play mp3 and dvd under Ubuntu install skype googleearth acroread and other stuffs using Medibuntu

First please install https://help.ubuntu.com/community/RestrictedFormats

You need to have extra repositories enabled..

Please first enable the universe and multiverse repository:

Open System → Administration → Software sources → [ Tab Ubuntu software ]

enable "Community-mainteined Open Source software ( universe )"
enable "Proprietary drivers for devices ( restricted )"
enable "Software restrictecd by copyright or legal issue ( multiverse )"

Close and confirm the repository reload.

Type the following command in a terminal (applications → accessories → terminal)

sudo aptitude install vlc

To get better dvd playback and optional packages here the medibuntu available software list http://packages.medibuntu.org/
you need to add the medibuntu http://www.medibuntu.org/ repository to your /etc/apt/sources.list file:
( here the medibuntu howto https://help.ubuntu.com/community/Medibuntu but see below )

In short type or better copy and paste the rows, below one row a time then press enter:

ubu_codename=$(sudo lsb_release -c | cut -d: -f 2 | sed 's/^[ \t]*//;s/[ \t]*$//')
sudo wget http://www.medibuntu.org/sources.list.d/$ubu_codename.list -O /etc/apt/sources.list.d/medibuntu.list
wget -q http://packages.medibuntu.org/medibuntu-key.gpg -O- | sudo apt-key add - && sudo apt-get update

Now to install, type:

sudo apt-get update
sudo apt-get install ubuntu-restricted-extras libxine1-ffmpeg
sudo aptitude install libdvdread3 libdvdnav4 libdvdcss2 regionset gnome-mplayer
sudo aptitude install non-free-codecs w32codecs
sudo aptitude install gstreamer0.10-pitfdll gstreamer0.10-plugins-good
sudo aptitude install gstreamer0.10-plugins-ugly gstreamer0.10-plugins-ugly-multiverse

give your user password when requested, you don't see nothing when you type it, then press enter.

You can also install other Medibuntu repository provided optional software http://packages.medibuntu.org/ :

sudo apt-get install skype
sudo apt-get install googleearth
sudo apt-get install acroread

Hope this helps