iText7追加模式下旋转页面数字签名显示异常求助

问题根源：你调用的page.SetIgnorePageRotationForContent(true)仅对页面原有内容的渲染生效，签名属于新增的表单注释外观，不受该设置影响。要修正旋转页面上的签名显示问题，需要直接针对PdfSignatureAppearance做配置。

方案1：让签名外观忽略页面旋转（保持原始方向） #

使用iText7为PdfSignatureAppearance提供的SetIgnorePageRotation(true)方法，该设置会直接作用于签名的layer2内容，使其不受页面旋转影响，始终以正常方向显示。

修改后的代码示例：

ItextTextPdf.PdfReader reader = new ItextTextPdf.PdfReader(stream);
using (MemoryStream ms = new MemoryStream())
{
    PdfWriter writer = new PdfWriter(ms);
    StampingProperties stamping = new StampingProperties().UseAppendMode();
    PdfSigner signer = new PdfSigner(reader, writer, stamping);
    PdfSignatureAppearance signatureAppearance = signer.GetSignatureAppearance();
    
    signatureAppearance.SetReason(Reason);
    signatureAppearance.SetLocation(Location); // 修正原代码笔误：将Reason改为Location
    
    Rectangle signRectangle = new iText.Kernel.Geom.Rectangle(llx, lly, width, height);
    var page = signer.GetDocument().GetPage(SignatureSettings.Page);
    
    // 移除无效的页面设置，改用签名外观专属的忽略旋转配置
    signatureAppearance.SetPageRect(signRectangle)
                      .SetPageNumber(SignatureSettings.Page)
                      .SetIgnorePageRotation(true); // 关键设置
    
    bouncyCastleCrypto.Org.BouncyCastle.X509.X509CertificateParser cp = new bouncyCastleCrypto.Org.BouncyCastle.X509.X509CertificateParser();
    bouncyCastleCrypto.Org.BouncyCastle.X509.X509Certificate[] pk = new bouncyCastleCrypto.Org.BouncyCastle.X509.X509Certificate[] { cp.ReadCertificate(cert.RawData) };
    signer.SignDetached(new AlliumDMSSigner.X509Certificate2Signature(cert, HashAlgorithmName), pk, null, null, null, 0, PdfSigner.CryptoStandard.CMS);
}

方案2：让签名外观跟随页面旋转（适配旋转方向） #

如果需要签名与页面旋转方向保持一致，可先获取页面旋转角度，调整签名矩形坐标或直接设置签名外观的旋转角度：

ItextTextPdf.PdfReader reader = new ItextTextPdf.PdfReader(stream);
using (MemoryStream ms = new MemoryStream())
{
    PdfWriter writer = new PdfWriter(ms);
    StampingProperties stamping = new StampingProperties().UseAppendMode();
    PdfSigner signer = new PdfSigner(reader, writer, stamping);
    PdfSignatureAppearance signatureAppearance = signer.GetSignatureAppearance();
    
    signatureAppearance.SetReason(Reason);
    signatureAppearance.SetLocation(Location);
    
    Rectangle signRectangle = new iText.Kernel.Geom.Rectangle(llx, lly, width, height);
    var page = signer.GetDocument().GetPage(SignatureSettings.Page);
    int pageRotation = page.GetRotation();
    
    // 方式1：调整签名矩形以适配页面旋转
    Rectangle rotatedRect = signRectangle.Rotate(pageRotation, page.GetPageSize());
    signatureAppearance.SetPageRect(rotatedRect).SetPageNumber(SignatureSettings.Page);
    
    // 方式2：直接设置签名外观的旋转角度，与页面保持一致
    // signatureAppearance.SetRotation(pageRotation);
    
    bouncyCastleCrypto.Org.BouncyCastle.X509.X509CertificateParser cp = new bouncyCastleCrypto.Org.BouncyCastle.X509.X509CertificateParser();
    bouncyCastleCrypto.Org.BouncyCastle.X509.X509Certificate[] pk = new bouncyCastleCrypto.Org.BouncyCastle.X509.X509Certificate[] { cp.ReadCertificate(cert.RawData) };
    signer.SignDetached(new AlliumDMSSigner.X509Certificate2Signature(cert, HashAlgorithmName), pk, null, null, null, 0, PdfSigner.CryptoStandard.CMS);
}

内容的提问来源于stack exchange，提问作者mihai stoica