DynaPDF Manual - Page 205
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changes are appended to the end of the file, leaving its original contents intact. This technique is
required since altering any existing bytes in the file invalidates existing signatures.
However, incremental updates are not supported by DynaPDF that is why only empty signature
fields are imported. Because DynaPDF creates always a completely new PDF file, it makes no sense
to import existing signatures, they would become invalid.
Possible function errors
When trying to sign a PDF file the function must first parse the certificate file before a signature can
be created. This process can fail, due to an invalid file path or due to an unsupported certificate file
format that was passed to the function. The PDF file will be closed and signed if the certificate file
was valid and no other error occurred during the parsing process of the certificate file.
If an error occurred during the parsing process, e.g. invalid certificate file, invalid file path and so
on, the function returns zero and passes an error message to the error callback function if any. All
errors during the parsing process of the certificate file are non-fatal so that the PDF file is still in
memory when the function returns. It is then possible to change the certificate file and trying to sign
the PDF file again.
To determine whether the PDF was already deleted or of it is still in memory call the function
HaveOpenDoc(). The function returns true if the PDF file is in memory. If the function returns false,
the last error was fatal and the PDF file has already been deleted.
The buffer of a memory based PDF file can be returned by GetBuffer() after this function was called.
Note that GetBuffer() does not free the used resources because it returns a pointer to the original
buffer. After the buffer was processed by your application call FreePDF() to free the uses resources.
See also CreateSigFieldAP(), CreateNewPDF(), GetBuffer(), FreePDF().
Further information about digital signatures can be found under Digital Signatures. The appearance
of a signature field can be user defined. See CreateSigFieldAP() for further information.
If the function succeeds the return value is 1. If the function fails the return value is 0.
const PPDF* IPDF,
// Instance pointer
struct TPDFSigParms* SigParms) // Important parameters
htDetached, // Byte ranges of the finish PDF file will be returned
// The SHA1 hash to be signed will be returned
Previous topic: CloseAndSignFileEx, Importing signed PDF files
Next topic: Supported PKCS#7 Format, Hardware Certificates