Once in a while you need to deal with fancier PDF files which may allow you to type in using forms, but Linux applications like Okular might not be fully capable of handling Adobe’s proprietary features. In such an unfortunate event, you might need to use Adobe Reader.

Go to the FTP download site on Adobe and download the version you wish to install. Here the version 9.x is assumed:

$ wget ftp://ftp.adobe.com/pub/adobe/reader/unix/9.x/9.5.5/enu/AdbeRdr9.5.5-1_i386linux_enu.deb
$ sudo dpkg --add-architecture i386
$ sudo apt-get update
$ sudo apt-get install libgtk2.0-0:i386 libxml2:i386 libstdc++6:i386
$ sudo dpkg -i AdbeRdr9*.deb

If the installation doesn’t fully complete, you might need to do

$ sudo apt-get -f install

to install the rest of missing packages.