Thanks a million Mariusz, I will try this solutions :)

@Mariusz, I have checked in my system, its the same revision installed currently in my system which you mention (0.12.1 (with patched qt)). If I have normal description on line like2,3 line description than it works well till number of pages reports, but I have more description on product detail it start causing problem, my is very worst case, product may have description of 1 page.and that description needs to be printed on report.

After many tries for better understanding of usage of wkhtmltopdf I suppose that you should decrease font size for body. In my opinion exceeding the dimensions of body has more importance than header. In process of generation qweb reports odoo has many defined parameters for rendering pages. In my tests when step by step I increased font size, at some the moment I had ugly pages: without header or footer. It looked as pages have lost header or footers. BTW wkhtml in newest version 0.12.2.1 (qt patched) still is not good...