Problem in merging pdf files using the itext library

[sn omen]

I want to merge few pdf files stored in the device' sdcard.
I'm able to merge the pdf files, if the total size of the pdf files is 35Mb.
But if add one more pdf file and try merging I'm getting the following error.

    02-23 18:11:33.586: W/dalvikvm(4365): threadid=1: thread exiting with uncaught exception (group=0x40018578)
    02-23 18:11:33.625: E/AndroidRuntime(4365): FATAL EXCEPTION: main
    02-23 18:11:33.625: E/AndroidRuntime(4365): java.lang.OutOfMemoryError
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at java.io.ByteArrayOutputStream.toByteArray(ByteArrayOutputStream.java:122)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.itextpdf.text.io.StreamUtil.inputStreamToArray(StreamUtil.java:77)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.itextpdf.text.io.RandomAccessSourceFactory.createSource(RandomAccessSourceFactory.java:146)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:350)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.itextpdf.text.pdf.PdfReader.<init>(PdfReader.java:370)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.example.pdf.MergePDF.concatPDFs(MergePDF.java:62)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.example.pdf.MergePDF.combine(MergePDF.java:40)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.example.pdf.FirstActivity.onCreate(FirstActivity.java:24)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1615)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1667)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.ActivityThread.access$1500(ActivityThread.java:117)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:935)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.os.Handler.dispatchMessage(Handler.java:99)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.os.Looper.loop(Looper.java:130)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at android.app.ActivityThread.main(ActivityThread.java:3687)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at java.lang.reflect.Method.invokeNative(Native Method)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at java.lang.reflect.Method.invoke(Method.java:507)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
    02-23 18:11:33.625: E/AndroidRuntime(4365): 	at dalvik.system.NativeStart.main(Native Method)

Below is the class file used for merging the pdf file.

    public class MergePDF {
    	static String mPath;
    
    	public void combine(String path) {
    		{
    			mPath = path;
    			try {
    				List<InputStream> pdfs = new ArrayList<InputStream>();
    
    				File _folder = new File(path);
    				File[] filesInFolder;
    				filesInFolder = _folder.listFiles();
    
    				for (File string : filesInFolder) {
    					pdfs.add(new FileInputStream(string));
    				}
    				if(new File(path + "merge.pdf").exists()){
    					new File(path + "merge.pdf").delete();
    				}
    				OutputStream output = new FileOutputStream(path + "merge.pdf");
    				MergePDF.concatPDFs(pdfs, output, true);
    
    			} catch (Exception e) {
    
    			}
    		}
    	}
    
    	public static void concatPDFs(List<InputStream> streamOfPDFFiles,
    			OutputStream outputStream, boolean paginate) {
    
    		Document document = new Document();
    		InputStream pdf = null;
    		try {
    			List<InputStream> pdfs = streamOfPDFFiles;
    			List<PdfReader> readers = new ArrayList<PdfReader>();
    			int totalPages = 0;
    			Iterator<InputStream> iteratorPDFs = pdfs.iterator();
    
    			// Create Readers for the pdfs.
    			while (iteratorPDFs.hasNext()) {
    				pdf = iteratorPDFs.next();
    				PdfReader pdfReader = new PdfReader(pdf);
    				readers.add(pdfReader);
    				totalPages += pdfReader.getNumberOfPages();
    			}
    			// Create a writer for the outputstream
    			PdfWriter writer = PdfWriter.getInstance(document, outputStream);
    
    			document.open();
    			BaseFont bf = BaseFont.createFont(BaseFont.HELVETICA,
    					BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
    			PdfContentByte cb = writer.getDirectContent(); // Holds the PDF
    			// data
    
    			PdfImportedPage page;
    			int currentPageNumber = 0;
    			int pageOfCurrentReaderPDF = 0;
    			Iterator<PdfReader> iteratorPDFReader = readers.iterator();
    
    			// Loop through the PDF files and add to the output.
    			while (iteratorPDFReader.hasNext()) {
    				PdfReader pdfReader = iteratorPDFReader.next();
    
    				// Create a new page in the target for each source page.
    				while (pageOfCurrentReaderPDF < pdfReader.getNumberOfPages()) {
    					document.newPage();
    					pageOfCurrentReaderPDF++;
    					currentPageNumber++;
    					page = writer.getImportedPage(pdfReader,
    							pageOfCurrentReaderPDF);
    					cb.addTemplate(page, 0, 0);
    					
    					// Code for pagination.
    					if (paginate) {
    						cb.beginText();
    						cb.setFontAndSize(bf, 9);
    						cb.showTextAligned(PdfContentByte.ALIGN_CENTER, ""
    								+ currentPageNumber + " of " + totalPages, 520,
    								5, 0);
    						cb.endText();
    					}
    				}
    				pageOfCurrentReaderPDF = 0;    				 
    			}
    			outputStream.flush();
    			document.close();
    			outputStream.close();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			if (document.isOpen())
    				document.close();
    			try {
    				if (outputStream != null)
    					outputStream.close();
    			} catch (IOException ioe) {
    				ioe.printStackTrace();
    			}
    		}
    	}
    }

The library that I'm using to merge the pdf is itext.