PDPage page = (PDPage)pagesIter.next();
            COSBase contents = page.getCOSDictionary().getDictionaryObject( COSName.CONTENTS );
            PDResources resources = page.findResources();
            if( resources == null )
            {
                resources = new PDResources();
                page.setResources( resources );
            }
            COSDictionary res = resources.getCOSDictionary();

            if( contents instanceof COSStream )
            {
                COSStream stream = (COSStream) contents;
                Map objectNameMap = new TreeMap();
                stream = makeUniqObjectNames(objectNameMap, stream);

                layoutPages.add(new LayoutPage(stream, res, objectNameMap));
            }
            else if( contents instanceof COSArray )
            {
                throw new UnsupportedOperationException("Layout pages with COSArray currently not supported.");
                // layoutPages.add(new LayoutPage(contents, res));
            }
            else
            {
                throw new IOException( "Contents are unknown type:" + contents.getClass().getName() );
            }
        }
    }

    private COSStream makeUniqObjectNames(Map objectNameMap, COSStream stream) throws IOException
    {
        ByteArrayOutputStream baos = new ByteArrayOutputStream(10240);

        byte[] buf = new byte[10240];
        int read;
        InputStream is = stream.getUnfilteredStream();
        while ((read = is.read(buf)) > -1)
        {
            baos.write(buf, 0, read);
        }

        buf = baos.toByteArray();
        baos = new ByteArrayOutputStream(buf.length + 100);
        StringBuffer sbObjectName = new StringBuffer(10);
        boolean bInObjectIdent = false;
        boolean bInText = false;
        boolean bInEscape = false;
        for (int i = 0; i<buf.length; i++)
        {
            byte b = buf[i];

            if (!bInEscape)
            {
                if (!bInText && b == '(')
                {
                    bInText = true;
                }
                if (bInText && b == ')')
                {
                    bInText = false;
                }
                if (b == '\\')
                {
                    bInEscape = true;
                }

                if (!bInText && !bInEscape)
                {
                    if (b == '/')
                    {
                        bInObjectIdent = true;
                    }
                    else if (bInObjectIdent && Character.isWhitespace((char) b))
                    {
                        bInObjectIdent = false;

                        // System.err.println(sbObjectName);
                        // String object = sbObjectName.toString();

                        String objectName = sbObjectName.toString().substring(1);
                        String newObjectName = objectName + "overlay";
                        baos.write('/');
                        baos.write(newObjectName.getBytes());

                        objectNameMap.put(objectName, COSName.getPDFName(newObjectName));

                        sbObjectName.delete(0, sbObjectName.length());
                    }
                }

                if (bInObjectIdent)
                {
                    sbObjectName.append((char) b);
                    continue;
                }
            }
            else
            {
                bInEscape = false;
            }

            baos.write(b);
        }

        COSDictionary streamDict = new COSDictionary();
        streamDict.setItem(COSName.LENGTH, new COSInteger(baos.size()));
        COSStream output = new COSStream(streamDict, pdfDocument.getDocument().getScratchFile());
        output.setFilters(stream.getFilters());
        OutputStream os = output.createUnfilteredStream();
        baos.writeTo(os);
        os.close();

        return output;
    }

    private void processPages( List pages ) throws IOException
    {
        Iterator pageIter = pages.iterator();
        while( pageIter.hasNext() )
        {
            PDPage page = (PDPage)pageIter.next();
            COSDictionary pageDictionary = page.getCOSDictionary();
            COSBase contents = pageDictionary.getDictionaryObject( COSName.CONTENTS );
            if( contents instanceof COSStream )
            {
                COSStream contentsStream = (COSStream)contents;
                // System.err.println("stream");
                pageCount++;

                COSArray array = new COSArray();

                array.add(contentsStream);

                mergePage( array, page );

                pageDictionary.setItem(COSName.CONTENTS, array);
            }
            else if( contents instanceof COSArray )
            {
                COSArray contentsArray = (COSArray)contents;

                mergePage( contentsArray, page );
            }
            else
            {
                throw new IOException( "Contents are unknown type:" + contents.getClass().getName() );
            }
        }
    }

    private void mergePage(COSArray array, PDPage page )
    {
        int layoutPageNum = pageCount % layoutPages.size();
        LayoutPage layoutPage = (LayoutPage) layoutPages.get(layoutPageNum);
        PDResources resources = page.findResources();
        if( resources == null )
        {
            resources = new PDResources();
            page.setResources( resources );
        }
        COSDictionary docResDict = resources.getCOSDictionary();
        COSDictionary layoutResDict = layoutPage.res;
        mergeArray(PROC_SET, docResDict, layoutResDict);
        mergeDictionary(COSName.FONT, docResDict, layoutResDict, layoutPage.objectNameMap);
        mergeDictionary(XOBJECT, docResDict, layoutResDict, layoutPage.objectNameMap);
        mergeDictionary(EXT_G_STATE, docResDict, layoutResDict, layoutPage.objectNameMap);

        //we are going to wrap the existing content around some save/restore
        //graphics state, so the result is
        //
        //<save graphics state>
        //<all existing content streams>
        //<restore graphics state>
        //<overlay content>
        array.add(0, saveGraphicsStateStream );
        array.add( restoreGraphicsStateStream );
        array.add(layoutPage.contents);
    }

    /**
     * merges two dictionaries.
     *
     * @param dest
     * @param source
     */
    private void mergeDictionary(COSName name, COSDictionary dest, COSDictionary source, Map objectNameMap)
    {
        COSDictionary destDict = (COSDictionary) dest.getDictionaryObject(name);
        COSDictionary sourceDict = (COSDictionary) source.getDictionaryObject(name);

        if (destDict == null)
        {
            destDict = new COSDictionary();
            dest.setItem(name, destDict);
        }
        if( sourceDict != null )
        {

            Iterator iterKeys = sourceDict.keyList().iterator();
            while (iterKeys.hasNext())
            {
                COSName key = (COSName) iterKeys.next();
                COSName mappedKey = (COSName) objectNameMap.get(key.getName());
                if (mappedKey == null)
                {
                    // object not needet
                    continue;
                }

                destDict.setItem(mappedKey, sourceDict.getItem(key));
            }
        }
    }

    /**
     * merges two arrays.
     *
     * @param dest
     * @param source
     */
    private void mergeArray(COSName name, COSDictionary dest, COSDictionary source)
    {
        COSArray destDict = (COSArray) dest.getDictionaryObject(name);
        COSArray sourceDict = (COSArray) source.getDictionaryObject(name);

        if (destDict == null)
        {
            destDict = new COSArray();
            dest.setItem(name, destDict);
        }

        for (int sourceDictIdx = 0; sourceDict != null && sourceDictIdx<sourceDict.size(); sourceDictIdx++)
        {
            COSBase key = sourceDict.get(sourceDictIdx);
            if (key instanceof COSName)
            {
                COSName keyname = (COSName) key;

                boolean bFound = false;
                for (int destDictIdx = 0; destDictIdx<destDict.size(); destDictIdx++)
                {
                    COSBase destkey = destDict.get(destDictIdx);
                    if (destkey instanceof COSName)
                    {
                        COSName destkeyname = (COSName) destkey;
                        if (destkeyname.equals(keyname))
                        {
                            bFound = true;
                            break;
                        }
                    }
                }
                if (!bFound)
                {
                    destDict.add(keyname);
                }
            }
        }
    }
}