Update 3/28/18: This appears to be fixed in the newer KiCAD libraries, and probably has been for some time.

KiCAD's default collection of libraries has an issue in the connect footprint library, including the set of SIL footprints. (The SIL footprints are usually used for things like headers). In short, many manufacturers recommend 1mm diameter holes. KiCAD uses holes just slightly bigger than 0.8mm. This is not an academic issue - it caused problems for me! A manufacturer-recommended footprint looks like this:

In truth, 0.8mm holes should work, but may not due to variations in hobbyist-level manufacturing. I've had boards come back that don't work because of this! I made a mistake. Hopefully you won't.

Here's an example KiCAD footprint library fixing this issue. I've only done SIL-1 through SIL-8, but you can extend this to bigger SIL packages, as well as packages meant to fit headers with multiple rows. An example of my fixed footprints looks like this: