PDFill is an editing and creation tool for PDF documents with which you can add, modify, and eliminate information in a new or previously existing document.
The options it offers are numerous, and include text insertion, links, images, comments, forms, and all sorts of information typical of these kids of documents.
Additionally, it offers tools to scan documents and do some graphic editing. All of this and more make PDFill an option that's worth your time to try out.
Documents created with the editor will have a watermark.