A very good example of how to style a WPF TabControl.
From Brandon Cannaday at Switch on the code.
I use this Style to surround each TabItem Content with a ScrollViewer:
<Style TargetType="{x:Type TabControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TabControl}">
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<TabPanel Grid.Row="0" IsItemsHost="True" />
<ScrollViewer Grid.Row="1"
VerticalScrollBarVisibility="Auto"
Margin="5,5,5,5"
Background="White">
<ContentPresenter ContentSource="SelectedContent" />
</ScrollViewer>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>