Format
The message is read on a phone, in between other chats. Write it in two short blocks: in the first, who you are and one detail from the conversation; in the second, the request. If the person has not saved your number yet, your name and your company must be in the first line, or the message looks like it came from a stranger.
Send voice notes only if the person has already sent you one. Catalogs and PDF presentations can wait until the first reply: in a first contact, an attachment without context is more weight than help.