Look in the FAQ for this group, you'll find a link.
One of those takes you to a source for some pretty old manuals (by todays standards anyway)and the other link, which used to provide free & open access to all the latest Mitel stuff now is limited to registered Mitel customers and VARs.
I've never seen an online source for Octel manuals.
What is it you're needing (or needing help with)?