I'm using following code (C#) to determine the number of pages in doc and docx 
files: 

Code: 
public static short GetPageCount(string path) 
      { 
         if (_componentLoader == null) 
            Initialize(); 

         XComponent xComponent = null; 
         int counter = 0; 

         while (xComponent == null) 
         { 
            try 
            { 
               string url = _urlConverter.getFileURLFromSystemPath
(Path.GetPathRoot(path), path); 
               xComponent = _componentLoader.loadComponentFromURL
(url, "_blank", 0, new PropertyValue[] { MakePropertyValue("Hidden", new uno.Any
(true)) }); 
            } 
            catch (DisposedException) 
            { 
               if (counter >= _maxRetries) 
                  throw; 

               Thread.Sleep(200 * counter); 
               Initialize(); 
            } 
            finally 
            { 
               counter++; 
            } 
         } 

         XTextDocument doc = (XTextDocument)xComponent; 
         XController controller = doc.getCurrentController(); 
         XPageCursor cursor = (XPageCursor)((XTextViewCursorSupplier)
controller).getViewCursor(); 

         cursor.jumpToLastPage(); 
         short result = cursor.getPage(); 

         return result; 
      } 

The purpose of Initialize and MakePropertyValue methods is evident.

Result is sometimes different then the actual number of pages (as rendered by 
swriter). The only workaround I've found is not specifying Hidden property when 
loading xComponent. It's not acceptable for many reasons.