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DynaPDF Manual - Page 182

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Function Reference
Page 182 of 750
Return values:
If the function succeeds the return value is 1. If the function fails the return value is 0.
CloseAndSignFileEx
Syntax:
SI32 pdfCloseAndSignFileEx(
const PPDF* IPDF,
// Instance pointer
const char* OpenPwd,
// Optional Open password
const char* OwnerPwd,
// Optional Owner password
TKeyLen KeyLen,
// Key length (40 or 128 bit)
TRestrictions Restrict, // Restrictions
const char* CertFile,
// File path to a PKCS#12 certificate file
const char* Password,
// Password to decrypt the cert's private key
const char* Reason,
// Optional reason string
const char* Location)
// Optional signers location string
This function finishes the PDF file, encrypts it, digitally signs it, and frees all used resources if the file
was not created in memory. The first five parameters have the same meaning as of the function
CloseFileEx(). The remaining parameters are identical to CloseAndSignFile(). This function simply
combines both functions because a PDF file must be encrypted and digitally signed in one pass. The
encryption parameters are described in detail under CloseFileEx().
The parameter CertFile must be a valid path to a PKCS#12 certificate file. DynaPDF supports
certificate files with 1024 bits encrypted private keys only. The parameter Password holds the
password to decrypt the private key. The parameters Reason and Location are both optional. These
strings are printed into the signature field if set.
Digital signatures are stored in a signature field which is a special type of Interactive Form field. If
no signature field exist when the function is called then DynaPDF creates an invisible signature field.
Hidden signature fields appear in the signatures tab of Adobe's Acrobat.
If one or more signature fields exist when the function is called then the first signature field is used
for signing. Signature fields can be created with the function CreateSigField() but it is also possible to
import empty signature fields from an external PDF file.
Importing signed PDF files
Signed PDF files can only be changed, without invalidating an existing signature, when changes are
stored with an incremental update. An incremental update is a special way to modify a PDF file;
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.
 

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