網上看到得，改了很少得部分

public static void main(String[] args) {

partitionPdfFile("/Users/shuguang/Desktop/pdf/九型人格.pdf");

}

private static int N = 0;
private static final int pageSize = 5;//每五頁作為一個新得pdf

public static void partitionPdfFile(String filepath)
{
Document document = null;
PdfCopy copy = null;

try
{
PdfReader reader = new PdfReader(filepath);

int n = reader.getNumberOfPages();
if(n%pageSize!=0){
N = n/pageSize+1;
}else{
N = n/pageSize;
}

if(n < N)
{
System.out.println("The document does not have " + N + " pages to partition !");
return;
}

int size = pageSize;
String staticpath = filepath.substring(0, filepath.lastIndexOf("\\")+1);
String savepath = null;
ArrayList<String> savepaths = new ArrayList<String>();
for(int i=1; i<=N; i++)
{ //獲取分批得pdf檔案得路徑陣列
if(i < 10)
{
savepath = filepath.substring(filepath.lastIndexOf("\\")+1, filepath.length()-4);
savepath = staticpath + savepath + "0" + i + ".pdf";
savepaths.add(savepath);
}
else
{
savepath = filepath.substring(filepath.lastIndexOf("\\")+1, filepath.length()-4);
savepath = staticpath + savepath + i + ".pdf";
savepaths.add(savepath);
}
}

for(int i=0; i<N-1; i++)
{//生成除最後一個pdf得pdf檔案
document = new Document(reader.getPageSize(1));
copy = new PdfCopy(document, new FileOutputStream(savepaths.get(i)));
document.open();
for(int j=size*i+1; j<=size*(i+1); j++)
{
document.newPage();
PdfImportedPage page = copy.getImportedPage(reader, j);
copy.addPage(page);
}
document.close();
}

//最後一個檔案單獨處理，怕有頁數不滿足特定頁數得需求
document = new Document(reader.getPageSize(1));
copy = new PdfCopy(document, new FileOutputStream(savepaths.get(N-1)));
document.open();
for(int j=size*(N-1)+1; j<=n; j++)
{
document.newPage();
PdfImportedPage page = copy.getImportedPage(reader, j);
copy.addPage(page);
}
document.close();

} catch (IOException e) {
e.printStackTrace();
} catch(DocumentException e) {
e.printStackTrace();
}
}