I don't know why the beneficiaries would be asked to sign the trust, UNLESS they are also successor trustees, and even then, other than to get a specimen signature for banks, etc. to honor, it would not be needed and the specimen is typically done on papers other than the trust itself.
As for liens, if you are your own trustee, and want to refiance your mortgage, and have place your home in the trust, then the trustee needs to take out the mortgage, and it would be necessary to put a lien on the property for the mortgage to issue.
It also sounds to me as if this is a "do it yourself" trust. Those are usually a BAD idea as people often screw up when trying to do them, even with a computer program or form book.