Usually Ubuntu has newer versions than Debian, maybe your Ubuntu installation is aged.
If for some reason you can't update your Ubuntu, check this:
https://launchpad.net/~librecad-dev/+archive/ubuntu/librecad-stableWhen you paste your block to the canvas, it sits there. Select it by clicking, then you can Move, Rotate, Mirror, etc
You can edit blocks, open Block list, right click your block, select Edit block. Then you can dimension it, and change what you want. Be aware that it you have inserted this block many times, each of them is modified. But this is why blocks are used anyway :)