When you add "out" to the verb "send", it suggests that you are sending it to more than one person:

Did you get the revised schedule I sent out last week?

This phrase can be used in casual or business settings. In a very formal setting, you can use the phrase "distribute (something)" instead:

Did you receive the revised schedule that I distributed on March 7th?

Notice that "out" can come in two locations:

Send it out.

I sent them out.

Or:

I've already sent out the invitations.

Can you send out a reminder to all the sales staff?