Staffan,

I have seen your pdf and sample that you've sent in our developer network. Could you please repost them also in this forum? :-) 

The mess layout could be caused by your WebGrid Column itself because it has so many columns. When there are many columns, the layout would be resized automatically based on the paper size.

So, you have some options to customize your layout such as configure your font size, paper size, etc. You can also hide unnecessary columns you don't want to export.

e.g, with this code in Export event below:

        ((ISNet.WebUI.WebGrid.WebGridColumn)(((ISNet.WebUI.ISCollectionBase)(e.Table.Columns)).All[0])).Visible = false;

Unfortunately, I could not replicate your mess layout in my sample. But my sample will show you how I customize my own export layout. Hope this helps.

Regards,