I use the latest version of LibreOffice on Win 8.1.
Simplest idea: create a separate document with a page size matching the envelope and use the Mail Merge wizard to print the address on the envelope. I outlined the process in an answer to How do I create a document for all of my addressed envelopes?.
Of course, if you keep the envelope separate from your document, you need to print it separately and recombine it with the letter. Alternatively, you could print the addresses on labels and stick those on the envelopes.
Thanx! It seems very convoluted to have to do it that way. I only want to print names and addresses on some envelopes. There is no document associated with them. Word has a feature that makes it really easy. Thought LibreOffice might also.
Only printing some names and addresses on some envelopes could be pretty easy if you create a template once (or well, a document that contains the fields you want to print). After you only need to select the names/addresses that you want to print.