Is it safe to affix a watermark thanks to an online website on personal documents? [closed]
There are several ways to affix a watermark to a .pdf thanks to online websites. See for instance ilovepdf.com, tools.pdf24.org or one can search "add watermark to .pdf online" into his favourite search engine.
I am aware there exists several softwares to do it such as GIMP (GUI) or ImageMagick (Commandline) but as this is for a friend of me who is not so much into computer science, I wanted to know if he is safe using a website such as ilovepdf or tools.pdf24 to affix watermarks to several .pdf that contain sensitive personal informations such as ID Card picture or remuneration statements.
EDIT: This question is solved thanks to this French government website. I can not answer my question because it is closed, so I edited the question instead.
