is there a way to insert a signature on every post - even in other people's posts?

[benative]

i have a question VB Experts!
is there a way to pre write something like a link. and make it show up on every single post?
for example when people try to make a new post, there will be a link or other contents on the bottom. for example, it's just like the previous email showing up on the bottom when you reply to someone's email.