Add header and footer to locked page

Hi, we're trying to add headers and footers to locked pages.  
Long story short: We get about 300 pages of signed documents that we used a script on to flatten the documents then we could add headers and footers to the pages and save as a new PDF.  However, the addon is too old and does not work any longer.

Is there any other way to do this?  At present we are running "Optimize PDF" with a few settings and that works but it is not an ideal solution.  We would like to take the 300+ pages, keep them locked (either via saving as image or something), merge them all together, and add a footer (like page numbers, dates, etc...)