The PDF, by its nature, is a read-only format. Yeah, you got the Watermark On Pdf that allows you to modify it, etc.; and the Reader allows for some markup, but it was initially designed to be a global standard for read-only documents and/or digital forms that you can fill out. As such, people donât create documents in PDF â t create them in some other app (MS Word, Apple Pages, etc.) and then export them to PDF to be readable on any device. So what you need to do is add the watermark to your document in your designer app, and then export it to PDF together with the watermark. If you donât have access to the source document, only the PDF â then chances are you are not the creator of that PDF, so you donât really have any right to add a watermark to it. The above holds true for Mac, Windows, Linux, etc.
But even though it is true for other platforms, PDF is still a universal file format that can be read by almost anyone on all platforms. As an added safeguard, and to provide some extra protection to your PDF documents, you can donate it and ask that the PDF be locked by a digital signature. This makes sure that it cannot be altered (unlocked, added watermarks, etc.) once released, and is also a great way of keeping your PDF documents protected. Note also that a PDF file can either have the watermark or not. It just depends on the license that was applied when the source document was created. In most cases, the author of that PDF document would decide what is good for the PDF document. As such, by changing the “watermark” to a custom signature, the PDF is still read-only and not protected. As a result, you can.