预填充然后锁定

Question

我们有一个 PDF 表单库，其中包含可填写的字段，可以在 Adob​​e Reader 中打开并由我们的最终用户填写。请注意，我们不生成 PDF，而只是使用现有的 PDF。所有这些表单都受到保护，无法通过密码在 Acrobat 中编辑不可填写的字段。

问题在于，当我们在代码中打开 PDF 以预填充某些字段时，密码保护将丢失，并且提供的表单在 Acrobat 中是可编辑的。

所以：

1. 有没有办法在不解锁 PDF 和生成的输出流的情况下使用 iTextSharp 预填充可填充字段？
2. 有没有办法重新锁定表单，同时仍然允许最终用户 在 Reader 中打开、填写可填写字段、打印等，无需 需要密码？

这是我们当前使用的代码的简化示例。我们已尝试锁定输出流（代码当前不可用），但文件无法锁定，然后阅读器提示用户输入密码。

System.Text.ASCIIEncoding encoding = new System.Text.ASCIIEncoding();
Byte[] password = encoding.GetBytes("secretPassword");
PdfReader reader = null;
MemoryStream outputStream = null;
PdfStamper stamper = null;
pdfStream.Seek(0, SeekOrigin.Begin);
reader = new PdfReader(pdfStream, password);
outputStream = new MemoryStream();
stamper = new PdfStamper(reader, outputStream);

AcroFields fields = stamper.AcroFields;
fields.SetField("prefillField1", "Some text");
stamper.Close();
outputStream.Close();
reader.Close();
// outputStream sent to user/browser. PDF opens in Reader, but the form can be opened in 
// Acrobat without a password and edited.

Answer 1

如果 PDF 受密码保护，您将无法对其进行编辑。你会喜欢你必须用密码打开它来编辑它。这样看来，您正在创建该文档的副本并呈现给用户。您可以使用编辑密码加密 PDF。这是我发现与 itextsharp 一起使用的方法的副本。如果您设置editPassword 而将openPassword 保留为空，那么您的用户应该能够查看pdf 并与之交互，但将无法根据您设置的权限对其进行编辑。希望这会有所帮助。

    /// <summary>
    /// Adds the given Open (User) and Edit (Owner) password to the PDF and optionally sets
    /// the various Allow/Not Allowed restrictions
    /// </summary>
    /// <param name="openPassword">Open/User password</param>
    /// <param name="editPassword">Edit/Owner password</param>
    /// <param name="allowAssemply">Assembly means merging, extracting, etc the PDF pages</param>
    /// <param name="allowCopy">Copy means right-click copying the content of the PDF to the system</param>
    /// <param name="allowDegradedPrinting">Can print low quality version of the PDF</param>
    /// <param name="allowFillIn">Can insert data into any AcroForms in the PDF</param>
    /// <param name="allowModifyAnnotations">Modification of any annotations</param>
    /// <param name="allowModifyContents">Modification of any content in the PDF</param>
    /// <param name="allowPrinting">Allows printing at any quality level</param>
    /// <param name="allowScreenReaders">Allows the content to be parsed/repurposed for screen readers</param>
    public byte[] GetEncryptedPDF(byte[] pdf,
         string openPassword, string editPassword,
         bool allowAssemply, bool allowCopy,
         bool allowDegradedPrinting, bool allowFillIn,
         bool allowModifyAnnotations, bool allowModifyContents,
         bool allowPrinting, bool allowScreenReaders)
    {
        int permissions = 0;
        if (allowAssemply) 
            permissions = permissions | PdfWriter.ALLOW_ASSEMBLY;
        if (allowCopy) 
            permissions = permissions | PdfWriter.ALLOW_COPY;
        if (allowDegradedPrinting)  
            permissions = permissions | PdfWriter.ALLOW_DEGRADED_PRINTING; 
        if (allowFillIn) 
            permissions = permissions | PdfWriter.ALLOW_FILL_IN; 
        if (allowModifyAnnotations) 
            permissions = permissions | PdfWriter.ALLOW_MODIFY_ANNOTATIONS; 
        if (allowModifyContents) 
            permissions = permissions | PdfWriter.ALLOW_MODIFY_CONTENTS; 
        if (allowPrinting) 
            permissions = permissions | PdfWriter.ALLOW_PRINTING; 
        if (allowScreenReaders) 
            permissions = permissions | PdfWriter.ALLOW_SCREENREADERS; 

        PdfReader reader = new PdfReader(pdf);
        using (MemoryStream memoryStream = new MemoryStream())
        {
            PdfEncryptor.Encrypt(reader, memoryStream, true, openPassword, editPassword, permissions);
            reader.Close();
            return memoryStream.ToArray();
        }
    }