1) Strongly signed the project UnitTests.

2) Gave UnitTests internal access to DocX.dll 
DocX AssemblyInfo.cs
[assembly: InternalsVisibleTo("UnitTests")]

3) Updated target framework to .NET 4.0.

4) Fixed bug with InsertText() Formatting object was set to null by default, should have been new Formatting()

DocX/DocX.csproj

     <AppDesignerFolder>Properties</AppDesignerFolder>
     <RootNamespace>Novacode</RootNamespace>
     <AssemblyName>DocX</AssemblyName>
-    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkVersion>v4.0</TargetFrameworkVersion>
     <FileAlignment>512</FileAlignment>
     <SccProjectName>SAK</SccProjectName>
     <SccLocalPath>SAK</SccLocalPath>
     <StartupObject>
     </StartupObject>
     <SignAssembly>true</SignAssembly>
-    <AssemblyOriginatorKeyFile>
-    </AssemblyOriginatorKeyFile>
+    <AssemblyOriginatorKeyFile>StrongNameKey.pfx</AssemblyOriginatorKeyFile>
     <FileUpgradeFlags>
     </FileUpgradeFlags>
     <OldToolsVersion>3.5</OldToolsVersion>
     <IsWebBootstrapper>false</IsWebBootstrapper>
     <UseApplicationTrust>false</UseApplicationTrust>
     <BootstrapperEnabled>true</BootstrapperEnabled>
+    <TargetFrameworkProfile />
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>

DocX/Paragraph.cs

         /// </example>
         public Paragraph InsertParagraphBeforeSelf(string text)
         {
-            return InsertParagraphBeforeSelf(text, false, new Formatting());
+            return InsertParagraphBeforeSelf(text, false, null);
         }
 
         /// <summary>
         /// <param name="formatting">The text formatting.</param>
         public void InsertText(string value, bool trackChanges = false, Formatting formatting = null)
         {
+            // Default values for optional parameters must be compile time constants.
+            // Would have like to write 'public void InsertText(string value, bool trackChanges = false, Formatting formatting = new Formatting())
+            if (formatting == null) formatting = new Formatting();
+
             List<XElement> newRuns = HelperFunctions.FormatInput(value, formatting.Xml);
             Xml.Add(newRuns);
 
         /// <param name="formatting">The text formatting.</param>
         public void InsertText(int index, string value, bool trackChanges=false, Formatting formatting = null)
         {
+            #region Default values for optional parameters must be compile time constants.
+            // Would like to have written 'Formatting formatting = new Formatting())
+            if (formatting == null) formatting = new Formatting(); 
+            #endregion
+
             // Timestamp to mark the start of insert
             DateTime now = DateTime.Now;
             DateTime insert_datetime = new DateTime(now.Year, now.Month, now.Day, now.Hour, now.Minute, 0, DateTimeKind.Utc);

DocX/Properties/AssemblyInfo.cs

 [assembly: AssemblyCulture("")]
 
 // Allow the UnitTests to get at internal stuff.
-[assembly: InternalsVisibleTo("UnitTests")]
+[assembly: InternalsVisibleTo("UnitTests, PublicKey=00240000048000009400000006020000002400005253413100040000010001008f789f4c5e510820397a319f4470c971513778e65ad102a225ed5b204aef1c6750ba5086268afe54fc515e005447be038d89fdfa5f55935f83e0916a229956b36f0eabf7ea9b2ee2e216b9e63e40a715833a2e5c9c6944de97231dd792ebdc3132cef5c6e0d7160383d7a44ae39933cfaee0aa6ae9fe1175630f443bfce259b2")]
 
 // Setting ComVisible to false makes the types in this assembly not visible 
 // to COM components.  If you need to access a type in this assembly from 

UnitTests/UnitTests.csproj

     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
+  <PropertyGroup>
+    <SignAssembly>true</SignAssembly>
+  </PropertyGroup>
+  <PropertyGroup>
+    <AssemblyOriginatorKeyFile>StrongNameKey.pfx</AssemblyOriginatorKeyFile>
+  </PropertyGroup>
   <ItemGroup>
     <Reference Include="Microsoft.VisualStudio.QualityTools.UnitTestFramework, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL" />
     <Reference Include="System" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="UnitTest1.cs" />
   </ItemGroup>
-  <ItemGroup>
-    <ProjectReference Include="..\DocX\DocX.csproj">
-      <Project>{E863D072-AA8B-4108-B5F1-785241B37F67}</Project>
-      <Name>DocX</Name>
-    </ProjectReference>
-  </ItemGroup>
   <ItemGroup>
     <None Include="documents\Images.docx" />
     <None Include="documents\Paragraphs.docx" />
     <None Include="documents\Tables.docx" />
     <None Include="documents\Template.dotx" />
+    <None Include="StrongNameKey.pfx" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\DocX\DocX.csproj">
+      <Project>{E863D072-AA8B-4108-B5F1-785241B37F67}</Project>
+      <Name>DocX</Name>
+    </ProjectReference>
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it.