After adding watermark to a pdf file, I made the file as read only by the following code. The readonly pdf file can not been edited by adobe reader and foxit reader. But the readonly file can been edited by foxit pdf editor. The attachment is the readonly file I created and the editor I used.
Thanks for your inquiry. I have tested the scenario and noticed that shared PDF is editable using Foxit PDF Editor, so I have logged an issue in our issue tracking system as PDFNET-41123 and also linked your request to it. We will keep you updated via this thread regarding the issue status.
We are sorry for the inconvenience caused.
We have further investigated the issue and found that it is expected behavior in case of Foxit PDF Editor. Our API follows standards of Adobe Reader. The ticket is closed now.