DDX command for add or edit a text in static pdf



I'm able to retrieve a PDF in LC repository, to assemble with another pdf using Assembler DDX.

I would also add a line of text (or edit an existing one) in all the pages of pdf file to attach (for example, to insert the code of the document). This text may be inserted / modified either in the body as the header of the document, provided it is propagated on all pages of the document.

Can I perform a command such as DDX?

Has anyone another suggestion?