It says in my Trustee packet: Declaration Regarding Lack of Supporting Documents. What does this mean?

The Trustee packet consists of the documents that you should mail your trustee. When you file your bankruptcy forms, you'll receive information on exactly what the trustee requires from you and how they want you to send them their forms.

If you're able to send the trustee everything they require, then you don't need to send them the "Declaration Regarding Lack of Supporting Documents" as you're sending them every document they need. If you don't have all of the documents they requested, you can explain what's missing (and why) on this declaration. That way the trustee knows there's a reason you didn't include a document and you didn't just miss it.