registering a composition

[Francesco Petrogalli]

Hi all,

apologies in advance for the slightly off topic question, but after
doing my own research I am still unable to sort out how to publish a
composition.

I have written it with lilypond, but it hasn't been performed yet. I
wanted to secure the copyright before performing it. Given that there
is no performing artist yet, there is no recording, so I cannot
register it with ASCAP. Have I got this right?

What would be the standard way to "secure" the PDF when it is ready?

Thank you,

Francesco