in getView method set Tag for the checkbox holder.
holder.chkbox.setTag(object);
and inside onCheckedChanged do this
**public onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
Object obj = ( Object)buttonView.getTag();
holder.chkbox.setChecked(obj.isChecked() ? true : false);
documents.get(position).setChecked(obj.isChecked() ? true : false);
}**
This will help you get rid of that problem ;)