如何在Java中以编程方式减少PDF文件大小？

Document document = new Document(reader.getPageSizeWithRotation(1));
PdfCopy writer = new PdfCopy(document, new FileOutputStream(outFile));
document.open();
PdfImportedPage page = writer.getImportedPage(reader, ++i);
writer.setFullCompression();
writer.addPage(page);
document.close();
writer.close();

我使用iText分割和合并PDF，我需要你的帮助来减少（压缩）以编程方式输出PDF大小。请让我知道实现相同目标的步骤。

I am using iText to split and merger the PDF, I need your help to reduce (compress) the output PDF size programmatically. Please let me know the steps to achieve the same.