For an LLC in PA:
" A Certificate of Organization is required to be filed with the Bureau of Corporations and Charitable Organizations, accompanied by a docketing statement. "
See more and the links to those forms at http://www.portal.state.pa.us/portal/server.pt/community/corporation_bureau/12457/pennsylvania_limited_liability_company/571886
There are several other items mentioned on that page.
Certificate of Organization Domestic Limited Liability Company is what the LLC must file.
Please ask if you need more information or discussion.