how to install debug symbols

[Sam S.]

Ubuntu (which I assume you're talking about) apparently provides a
kdevelop-dbgsym package in in their debug symbol packages (ddebs)
repository.

How to use this repository is described in their wiki:
https://wiki.ubuntu.com/DebuggingProgramCrash

However, I have no idea how this plays together with package versions
from the "Unsupported Updates" (backports) repository, which you're
probably using for KDevelop.

As Milian pointed out, you'll have to ask the Ubuntu people directly -
try e.g. https://answers.launchpad.net/ubuntu