如何用密码保护已存在的PDF？ [英] How to protect an already existing PDF with a password?

问题描述

如何设置现有PDF的密码？

How to set password for an existing PDF?

推荐答案

你看过 EncryptionPdf 我书中第12章的例子？

Did you look at the EncryptionPdf example in chapter 12 of my book?

就这么简单：

public void encryptPdf(String src, String dest) throws IOException, DocumentException {
    PdfReader reader = new PdfReader(src);
    PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest));
    stamper.setEncryption(USER, OWNER,
        PdfWriter.ALLOW_PRINTING, PdfWriter.ENCRYPTION_AES_128 | PdfWriter.DO_NOT_ENCRYPT_METADATA);
    stamper.close();
    reader.close();
}

请注意 USER 和 OWNER 的类型为 byte [] 。您有不同的权限选项（查找以 ALLOW _ 开头的常量），您可以选择不同的加密算法。

Note that USER and OWNER are of type byte[]. You have different options for the permissions (look for constants starting with ALLOW_) and you can choose from different encryption algorithms.

至于参数： src 是现有PDF的路径。 dest 是加密PDF的路径。很明显，在阅读文件时无法写入文件。这在此解释：如何在不创建的情况下更新PDF一个新的PDF？

As for the parameters: src is the path to the existing PDF. dest is the path of the encrypted PDF. It should be obvious that you can not write to a file while you are reading it. That is explained here: How to update a PDF without creating a new PDF?

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