Again you don’t want buy license for Adobe acrobat PDF creator/editor and don’t want the free alternative software to add their watermark after editing your document.
I found several online free services but most of them were just capable of re-arranging pages and drawing shapes on the white area.
I consider http://www.pdfescape.com/ is the best among all available free services which give more flexibility while editing PDF online.
Other sire offering Free PDF editing online are
Acrobat.com (Only Creation )