Security settings not followed when signed

It seems, security settings are not adhered to when also signing.

If a pdf-file is not being signed, the security setings are as set in the options panel. If the pdf is signed however, everything is allowed, where it should be forbidden.

Assume this is a bug, as I can't imagine it is meant as a feature.

(Checked with both Windows XP(SP3) and Windows 98.)