I need to take a PDF, add some dynamically generated license text to it, and digitally sign the document before emailing it to the intended recipient. What's the best way to do this in PHP?
My understanding of digital signage is that the content of the PDF is converted into a hash, and some property of the document is set to this value. If the content when converted to a hash doesn't match the hash in that property, the document has been altered. Is this correct? What is the certificates discussed on this and this page?
Am I right to think that it isn't possible to edit an existing PDF with TCPDF, only to create a new one? Is SetaPDF Stamper and SetaPDF Signer a valid and good option?
Many thanks