A PDF (Portable Document Format) was intended to be a file format that made sharing it safe and easy. If you created a PDF file, then when you share it with other people it makes it more difficult for them to edit your work. There are ways around this. If you do not have Adobe software, then this link provides information how to edit a PDF with a free web app. Apparently, you can also edit a PDF from Word! Here is how.
Hope this helps!