After you file

Here are the answers;

Must the papers being mailed be stapled? Is a binder clip acceptable? Stapled only.

Intuit's "Electronic Postmark - Certification of Electronic Filing" was printed with the federal return - does this also need to be mailed?  No the e-filing stamp is unnecessary.

For federal - only the form 1040X has to be signed? There doesn't seem to be any area to sign on the attached 1040 Sign only the 1040X.

For California - only form 540 has to be signed? There seems to be no signature required for Schedule X. Sign the 540.

California requires attaching a copy of the federal return - does this copy of the federal return need to be signed? If so, does it require a photo copy of the actual signatures on the federal return or can it be wet signed? Attach copy of the Federal return and it does not have to be signed.