PDFs are a great way to send out a document knowing that it anyone will be able to see the document as you indented and won’t be able to make their own changes to it.  But, if you loose the original document and want to make some changes to your PDF yourself you’ll find yourself in quite a pickle.  Thankfully there are some free PDF converters available online, the one I’ve had the most success with is PDF-to-Word.

http://www.pdftoword.com/

Also, there’s another useful online application that will let you quickly merge two PDFs together

http://www.mergepdf.net/