I'm using odoo v8 and I have wkhtmltopdf 0.12.1 (with patched qt) but the header line is overlapping text on second page, it is fine on first page, Im attaching image to show you the error.
https://s31.postimg.org/gm6zwgcqz/report_header.jpg
You can see the line from the header is overlapping the (Sample text)