Do you "own" a licensed iso of Windows 8.1? That is, one that you have paid for, as Windows and other Microsoft products are proprietary and not free. (OK, you just pay for the license to use it!)
If so...
Any of the CD/DVD burning software included in Ubuntu or Mint, e.g. Brasero, K3b, etc. would then be able to produce a bootable CD/DVD.
Does that answer your question?
If you're trying to rip off and copy Windows 8.1 which is illegal, we can't help you.
Oh! and try not to double post.
Play Bonny!
