In my test app, the document labels are too tight. Selecting a secondary document tab, then reselecting the original one, fixes the problem.
Attached is a 'before' image.
John
The problem sounds like an issue with the default styling so you should report that to the support group - http://ko.infragistics.com/gethelp/default.aspx#Overview. With regards to changing the default styles, the style for that particular item would be using a key of PaneTabItem.DocumentTabItemTemplateKey. Depending on the types of changes you are going to make, you may also need to alter the template for the tabgrouppane - the key for that style would be TabGroupPane.DocumentTabGroupTemplateKey.
Can someone at Infragistics point me in the right direction in the default styles files, to re-style the document tabs? I want to add a bigger margin to the textblock.