Monkeybread Software - DynaPDF Manual

DynaPDF Manual - Page 223

Function Reference

Page 223 of 860

Remarks:

Text objects are handled separately in PDF for use as clipping path. See SetTextDrawMode() for

further information.

Return values:

If the function succeeds the return value is 1. If the function fails the return value is 0.

CloseAndSignFile

Syntax:

SI32 pdfCloseAndSignFile(

const PPDF* IPDF,

// Instance pointer

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, digitally signs it, and frees all used resources if the file was not

created in memory. The parameter CertFile must be a valid path to a PKCS#12 certificate file.

DynaPDF signs PDF files on Windows with the Windows Crypt API. This signature handler

supports certificates with up to 4096 bits key length. Note that this function does not add a

timestamp to the signature. If a timestamp should be added then call CloseAndSignFileExt() with a

certificate handle instead.

On non-Windows systems the function uses the AiCrpyto library to sign PDF files. This signature

handler supports certificates with up to 1024 bits key lengths only. However, if certificates with a

stronger encryption should be used it is possible to sign the file with an external signature handler

(see CloseAndSignFileExt() for further information).

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 existing signatures, 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.

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