Word dose not let you do this and DocX aims to create documents that Word can open.

Big thanks to np83 not only for finding this bug but also posting a fix and unit tests.

When inserted into a Header or Footer Word will automatically display the correct value foreach page.

Word will not automatically update these place holders if inserted inside a document level Paragraph. 
You need to right click and select update field. I therefore suggest that you only use these place holders inside Headers and Footers.

Added
-------

Paragraph.AppendPageNumber(PageNumberFormat)
Paragraph.InsertPageNumber(PageNumberFormat, int index)

Paragraph.AppendPageCount(PageNumberFormat)
Paragraph.InsertPageCount(PageNumberFormat, int index)

Example
-----------
// Create a new document.
using (DocX document = DocX.Create(@"Test.docx"))
{
    // Add Headers to the document.
    document.AddHeaders();

    // Get the default Header.
    Header header = document.Headers.odd;

    // Insert a Paragraph into the Header.
    Paragraph p0 = header.InsertParagraph();

    // Append place holders for PageNumber and PageCount into the Header.
    // Word will replace these with the correct value foreach Page.
    p0.Append("Page (");
    p0.AppendPageNumber(PageNumberFormat.normal);
    p0.Append(" of ");
    p0.AppendPageCount(PageNumberFormat.normal);
    p0.Append(")");

    // Save the document.
    document.Save();
}

Below is a code example which uses the new Protection familiy of functions.

            // Load a document.
            using (DocX document = DocX.Load(@"Test.docx"))
            {
                if (document.isProtected)
                {
                    Console.WriteLine("Document is protected.");
                    Console.WriteLine("\tProtection type is " + document.GetProtectionType().ToString());
                    document.RemoveProtection();
                    Console.WriteLine("\tProtected removed.");

                    // Save the document.
                    document.Save();
                    Console.WriteLine("\tDocument saved as Test.docx");
                }

                else
                {
                    Console.WriteLine("Document is not protected.");
                    document.AddProtection(EditRestrictions.readOnly);
                    Console.WriteLine("\tProtected added.");
                    Console.WriteLine("\tProtection type is " + document.GetProtectionType().ToString());

                    // Save the document.
                    document.Save();
                    Console.WriteLine("\tDocument saved as Test.docx");
                }
            }

            // Wait until a user presses a key before exiting.
            Console.ReadKey();

-----------------
EditRestrictions 

DocX.cs
--------
EditRestrictions GetProtectionType()
AddProtection(EditRestrictions er)

---------
Added property bool isProtected
Added function removeProtection()

Protection is different than Encryption.

This fix checks that an element contains no drawing element and that its text length is zero before removing the element.

This projects contains many of the examples upload on my blog.
Each time docx is released, I will update these examples so as they still work regardless of API changes.

Added unit tests.
Depreciated overloads which confussed API.
Its now possible to create one Hyperlink and insert it into the main document, headers and footers.

Added unit tests.
Removed overloads which confussed API.
Its now possible to create one Picture and insert it into the main document, headers and footers.

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()

// Create a new document.
using (DocX document = DocX.Create(@"C:\Users\Cathal\Desktop\Hello.docx"))
{
    // Set this documents orientation to landscape and save.
    document.PageLayout.Orientation = Orientation.Landscape;
    document.SaveAs(@"Landscape.docx");

    // Set this documents orientation to portrait and save.
    document.PageLayout.Orientation = Orientation.Portrait;
    document.SaveAs(@"Portrait.docx");
}

Thank you for sharing your custom features with the group lckuiper.

Apparently <w:sectPr> tags can even be nested inside <w:Prp> tags and word will still open them.

Thanks to srwright for bringing this bug to my attention.

2:23 PM.

This patch adds the property VerticalAlignment to the Cell class.

Thank you for contributing this patch lckuiper.

Added bug fix for RemoveText when index is greater than possible.
Removed a few function overloads by utilising .NET 4.0 optional parameters.

br elements --\n-- should return size = 1

Added unit tests for Paragraph.RemoveHyperlink(int index)

    runLookup
    BuildRunLookup();

Added new unit tests for Paragraph.InsertHyperlink()

Image class now has FileName property.

Major new functions are listed below.

Paragraph
-----------
GetFirstRunEffectedByInsert()
GetFirstRunEffectedByInsertRecursive()

Run
----
GetFirstTextEffectedByInsert()
GetFirstTextEffectedByInsertRecursive()

HelperFunctions
-----------------
GetText
GetTextRecursive
GetSize(XElement Xml)

This new recursive search method does not return the same Paragraph multiple times thus the problem with Textbox's has also been fixed.

Paragraph p = document.InsertParagraph();
p.Append("Check out this ").Color(Color.Red).AppendHyperlink(h).Color(Color.Green).Append(", it's really cool").Color(Color.Blue);

Added getter and setter of document core properties for DocX.
Added unit test for ApplyTemplate.

Added Getter and Setter functions for Hyperlink. Also added Hyperlink properties for Document, Paragraph, Table, Row and Cell.

Added similar functions for Pictures.

Bug fix: Table.SetDirection(Direction) now changes the Direction of the Table and not just its contents.

----------
Created an abstract class called DocXElement and made every document element such as {Table, Row, Cell, Paragraph, Run, Text, etc} extend it.
Created an abstract class InsertBeforeOrAfter which is derived from DocXElement. This provides functions for inserting, page breaks, Paragraphs and Tables before and after self.
Moved Text and Run inside Paragraph, keep consistancy with Table which contains Row and Cell.
To Do: Investigated why the Picture class had two internal constructors. I removed one.
Added a _ to each .cs file that does not contain instanceable types, {Enumerations.cs, Extensions.cs, etc}

Bugs fixed
----------
Cell had a parameter Paragraph, this was incorrect as paragraphs can contain multiple Paragraphs. Now it returns a List<Paragraph>
InsertDocProperty now returns a DocProperty instead of void.

New features
------------
InsertDocProperty now contains overloads for the parameter track changes.
Cell now contains a Shading property, this can be used to set the background color of a cell.

Cathal: Added overloads to ReplaceText for Format checking and replacement.

Joel: Added Row.MergeCells
Joel: Added Row.Height property
Joel: Added Cell.Width property

A huge thanks to Joel: The first user to submit working & tested functions\properties for inclusion in DocX.

1) Paragraph.InsertPageBreakAfterSelf()
2) Paragraph.InsertPageBreakBeforeSelf()
3) Table.InsertPageBreakAfterSelf()
4) Table.InsertPageBreakBeforeSelf()