A simple bash script that inserts advertisement as 2nd page in all PDF files in a directory and its subdirectories. Depends on pdftk which is packaged in most distributions.
Simply put the page you want to insert as Page_Insert.pdf in the folder with the script and place the folder in the directory containing all the .PDFs you want modified. The script begins its search in the parent directory of the folder it is placed in, be sure to keep the script and Page_Insert.pdf in their own directory