Now I see.
Well, you cannot define the border line with HTML/CSS. But it is possible:
1. to define a page background image with a painted border line and to apply the image to all pages.
[language=Java:1rjzncx5]PD4PageMark footer = new PD4PageMark();
2. to create a static PDF page with a border line. It can be done from an HTML like the following:
(height value is to be adjusted there)
After that you could combine(underlay) the static PDF with your dynamically created PDF document.