在签署PDF时将签名放在同一页面上的多个位置 [英] Placing signature in multiple location on same page while signing a PDF
问题描述
我想在PDF中的多个位置放置相同的外部签名签名容器（签名值）。
我已经提到了页面'
请允许我重复此屏幕截图的最后一行：
签名字段永远不会引用多个注释。
这句话中有一个 ，不是应该的。应该不是规范性的。这意味着您应该或不应该做某些事情，但如果不这样做，您就不会违反规范。不尊重PDF文档中违反PDF规范的结果，严格意义上的结果不是真正的PDF文件。
这是一条路径你不想去，因为违反PDF规范会使您无权使用Adobe拥有的一系列PDF专利。 Adobe拥有可供所有人免费使用的专利（永久，非独家，免版税，......）条件您尊重ISO规范。
因此，除了建议放弃您的要求外，请不要期望回答您的问题。符合PDF规范的PDF查看器不会期望将单个签名放置在不同的位置，因为规范不允许这样做，因此即使您要调整软件以为单个签名创建多个窗口小部件注释/外观字段，无法保证PDF查看器能够理解您要执行的操作。
I want to place same externally signed signature container (signature value) at multiple places in a PDF.
I have referred the page 'How to place the Same Digital signatures to Multiple places in PDF using itextsharp.net'.
While working with the above mentioned work-around, I observed that whenever I tried to place multiple signatures on single page like 4-5 times, it never worked. Always shows only one valid signature field and other fields as unsigned (unsigned PDF form fields). So couldn't understand the problem.
Now I wanted to know whether any reference material is available to see how PdfLiteral and PdfIndirectReference works? I have gone through the itextsharp reference document but couldn't get enough information. In addition to this is there any limitation on how many annotations/signature fields one can add in a PDF? And If I have to use BlankSignatureContainer and MakeSignature.SignDeferred then how the signature will get attached to all the fields because in,
MakeSignature.SignDeferred(pdfreader, "Sig", output, externalcontainer)
we have to pass only one signature field name.
Thank you.
You are asking for something of which mkl wrote:
Beware: While this procedure creates something which does not violate the letter of the PDF specifications (which only forbid the cases where the same field object is referenced from multiple pages, be it via the same or via distinct widgets), it clearly does violate its intent, its spirit. Thus, this procedure might also become forbidden as part of a Corrigenda document for the specification.
Actually, what you are asking does violate the specification. See section 12.7.5.5 of the ISO standard for PDF:
Allow me to repeat the last line of this screen shot:
signature fields shall never refer to more than one annotation.
There is a shall in this sentence, not a should. A should isn't normative. It means that you should or shouldn't do something, but that you are not in violation with the spec if don't or do. Not respecting results in a PDF document that is in violation with the PDF specification, and that in the strict sense isn't a real PDF file.
That is a path you don't want to go, because being in violation with the PDF specification voids your right to use a series of PDF patents owned by Adobe. Adobe owns patents that can be used by everyone for free (perpetual, non-exclusive, royalty-free,...) on condition that you respect the ISO specification.
For that reason, please do not expect an answer to your question, except for the recommendation to abandon your requirement. PDF viewers that comply with the PDF specification won't expect a single signature to be placed at different locations because that's not allowed by the spec, so even if you would adapt your software to create more than one widget annotation / appearance for a single signature field, there is no guarantee that a PDF viewer will understand what you're trying to do.
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