使用 C# 使用密码锁定和解锁 PDF 文件
Let us learn to secure our documents from unauthorized access. Previously we discussed [adding text and image watermarks to the documents][1] to avoid and illegal use. In this article, we will see how to add password protection to PDF documents to get them locked using C#. Additionally, we will change the existing password and also learn to remove the password to make the PDF unlocked. 本文讨论了以下主题：
- .NET API 用于 PDF 文件的密码保护 * 通过添加密码锁定 PDF 文件 * 在 C# 中更改 PDF 密码 * 如何删除 PDF 密码 - 解锁 PDF