Every operating system has its own way to store preferences about associations of file types with programs. Mostly this is done by storing a list of MIME types linked with the programs that are able to open them, some use the file extensions instead. On nearly every system you are allowed to have multiple apps linked to a file type, and a preference which to launch first.
KDE allows you to associate applications with certains programs by using Konqueror/Settings menu/Konqueor settings/File associations. Search for a MIME type and edit the list of file extensions, the programs to be launched and their order, as well as the programs to use for embedding the file into the konqueror file view. Further, you can right-click on any file in Konqueror and have a "open with" submenu.
The preferences are stored locally in
~/.kde/share/mimelnk/*/*.desktop desktop files.
Global settings can be found in
/usr/kde/major.minor/share/mimelnk/*/*.desktop.