title: Show several FixedDocuments in a DocumentViewer, as if they were a single document
body: <p>In my WPF app, I have several <em>FixedDocument</em> objects, which I want to display together in a <em>DocumentViewer</em>, as if they were a single document.</p>
  
  <p>It's easy to display a single <em>FixedDocument</em> in a document viewer:</p>
  
  <pre><code>myDocumentViewer.Document = myFixedDocument;
  </code></pre>
  
  <p>My first idea was to create a <em>FixedDocumentSequence</em> of all my <em>FixedDocuments</em> (which can also be set as the <em>DocumentViewer.Document</em> value as it implements <em>IDocumentPaginatorSource</em>). But when building a <em>FixedDocumentSequence</em>, one can only add to a collection of <em>DocumentReference</em> objects. There is no straightforward way to add a <em>FixedDocument</em> directly, and I can't figure out how to create and add a <em>DocumentReference</em> which is somehow linked to one of my <em>FixedDocuments</em>.</p>
  
  <p>My second idea was to create a master <em>FixedDocument</em>, and then loop through all the <em>FixedDocuments</em>, and move their pages into the master <em>FixedDocument</em>. But I run into all sort of issues when trying to do this (to do with pages already belonging to another document (with no ability to remove them from that document! etc. etc.)</p>
  
  <p>My third idea was to create and build a temporary <em>XpsDocument</em>, and retrieve the <em>FixedDocumentSequence</em> that it automatically seems to create. I've looked at this a bit, but it's getting to be what feels needlessly complex, so I thought I'd post here first to see if there are any other ideas, or help with my first two attempts!</p>