This Camera was first supported in Lightroom 6.1.1.So raw files cannot be processed in Lightroom 5
Your options are to Upgrade to Lightroom 6/CC
or to Use DNG Converter to convert your files to DNG..See Photoshop Help | Adobe Digital Negative Converter 9.x
If the pixel-shifted images are JPEGs, LR 5 will handle them just fine.
Thanks for the advice. Pentax allows a choice of either PEF or DNG in camera, I always use DNG as it is more widely recognised.
I think I'll wait for LR7 before upgrading.
The advice to use DNG Converter on PSR (pixel shift resolution) files from the Pentax K-3II is wrong.
It will create a non-pixel shift DNG, which is NOT the same as the original DNG out of the camera. I suspect it just converts the first of four included images.
You could use the Digital Camera Utility that came with your camera to process them to a TIFF, or use a fork of dcraw to do so, tomtor/dcrawps: dcraw fork with Pentax Pixe... - GitHub
Lr CC does a quite nice job with them IMHO, however. If you go over to pentaxforums.com you can see some examples there.
Thanks Rob, are you saying I should use PEF when taking Pixelshifting?
I have been following Pentaxforums and indeed started a thread there, just wanted to get another perspective.
No, I'm saying use the DNG out of the camera. Or a JPEG. And Digital Camera Utility, which came with your camera since you don't seem to have other software to handle pixel shifted images. Or upgrade Lr or otherwise get Adobe Camera RAW in the latest version (like if you have Photoshop).