The absolute positioned div is indeed a big problem here for 2 reasons:
1) You dont specify top or left properties, so it will always go into the top left corner of the browser.
2) The z-index stacking order is dependent on the position attribute. but another way, there is a separate z-index stacking order for Absolutely positioned elements and Relative positioned elements. The Absolutely positioned stacking order is always on top of the relatively positioned elements
Regardless of setting the z-index for the relatively positioned element to 100, it will still be stacked under the absolutely positioned element, even with a z-index of -1
If you insist on giving the pdf div a position: absolute; you must specify a top and left attribute to position it on the page in a location that is not occupied by the menu.
As i explained in the previous post, position absolute requires that you provide absolute coordinates on the page for where you wish that element to be displayed. if no top and left coordinates are specified, top:0; and left:0; are used. this is directly over the menu.