GYLLY, I used to work at DWP (not a Jovcentre) and if we copied anything official for our use, we would note it as a "True" or "Certified" copy of the original but that was to show we had SEEN the original and returnt it.
That is fine for DWP use but if another organization needs to see a Certified Copy of an LPA, a Jobcentre stamp on a copy saying it's "certifified" would not be acceptable.
I'm not saying you shouldn't be doing it because it's not up to you what claimants/customers do with the copies you give them.
This link states who can certify copies
https://www.gov.uk/power-of-attorney/certify