为 PDF 添加数字签名
添加真实的加密签名，证明是谁签署了文件、文件此后未被更改——而不仅仅是一张签名图片。
使用方法
1. 上传你的 PDF。2. 当场创建一个免费签名，或上传你已有的证书（.pfx/.p12）。3. 下载——PDF 现在带有真实的数字签名，任何 PDF 阅读器都可以验证。
这与填写与签署有什么不同？
填写与签署只是把你签名的图片贴到页面上——看起来没问题，但没有任何机制能阻止别人在你不知情的情况下事后编辑文件。此工具嵌入的是真正的加密签名：任何 PDF 阅读器都能验证它，一旦签署后有哪怕一个字节被更改，就会标记出该文件。
两种签名方式有什么区别？
“创建免费签名”会当场生成一个与你填写的姓名和邮箱绑定的证书——它能证明文件在签署后未被篡改，但由于没有证书颁发机构为你的身份背书，PDF 阅读器会将其显示为未验证，除非有人选择信任它。“使用我的证书”允许你用已有的 .pfx/.p12 文件签名（例如用于报税、GST 或投标的印度 DSC 数字签名证书）——由于它是由受认可的机构签发的，信任该机构的阅读器会自动将签名显示为已验证。
自签名的签名具有法律效力吗？
这取决于你所在的国家和使用场景——从加密学角度看，它能证明文件的完整性（文件未被更改）以及签署人身份，但不像持牌证书颁发机构签发的签名那样自动具备同等法律效力。在用于合同或官方文件之前，请核实你所在地区的具体要求。
我的证书密码或私钥会被发送到任何地方吗？
不会——一切都在你的浏览器中完成。你的证书、密码和私钥永远不会离开你的设备。
Which laws actually recognize signatures like these?
Most countries have some law covering electronically signed documents — the US ESIGN Act and UETA, the EU's eIDAS regulation, India's IT Act 2000, and similar rules elsewhere. But these laws almost always draw a line between a signature backed by a certificate a recognized authority issued and one you generated yourself. A DSC signed with "Use my certificate" is the kind these laws were built around. A signature from "Create a free signature" cryptographically proves the file wasn't tampered with, but it doesn't get the same automatic recognition — treat it like any other self-signed certificate.
Can I send this to someone else to sign, or track multiple signers?
No — this tool signs a PDF that's already on your device, by you, right now. It doesn't email the file to anyone, collect signatures from other people, or give you a dashboard to track who's signed what. If you need to route a document to several signers and follow its status, you'll need a dedicated e-signature workflow service instead.
How does someone else verify the signature once I send them the file?
They open it in a PDF reader that checks digital signatures — Adobe Acrobat or Reader does this automatically and shows a signature panel with a checkmark or warning icon. Clicking it shows whether the document has changed since signing and who the certificate says signed it. If you signed with "Use my certificate" and the reader already trusts that CA, it shows as verified with no extra steps; a self-signed certificate shows as valid-but-unverified until the recipient chooses to trust it.