I just came across this PDF Reviewer who says:
*Are Free PDF Readers and Editors Secure?
I would strongly recommend against using a completely free PDF editor since the company has to find some way to make a profit, and you are most likely the product. Instead, take advantage of the Soda PDF free trial, which gives you unlimited access to its secure and safe PDF reader and editor. You can encrypt your files and add passwords to ensure that no one can open or view the files without your authorization."