I use wkhtmltopdf to produce A4 sized PDFs. When I create a height: 297mm; width: 210mm (which is the defined size
Perhaps try increasing the height of the <div> a fraction of a mm?
height: 297.5mm or height: 298mm instead?
Let me know if that works.
Try set <div> element style="margin: 0;" in my case this helps...
I had a method that worked for me that used margins.
style="margin:0,auto"
If that doesn't work try:
style="margin:0,auto,0,auto"