$ md5sum Documentos/ISOs/lubuntu-12.10-desktop-*
You can read the lines above as follows:
1) MD5 hash for lubuntu-12.10-desktop-amd64.iso is bddb521817360540c0e54616427c003e
2) MD5 hash for lubuntu-12.10-desktop-i386.iso is a7fed6c40b4969d4a3c9c0a9ee228cf2
With both hashes, access the page mentioned above and search for the name of ISO file. If the hash from the page is EXACTLY the same you got, so the file is okay, and you can make the correct use of it.
Make me know if it was somehow useful for you!