C Requires Chilkat v11.7.0+

Password-Protect a PDF with AES-256 Encryption

See more PDF Protection Examples

Demonstrates the simplest way to encrypt a PDF so that it needs a password to open. The passwords come from the UserPassword and OwnerPassword properties, and Protection with the encrypt operation and an empty JSON uses the defaults: AES-256, everything encrypted, every permission granted. Protection only records the security the PDF will be saved with. Nothing is encrypted until WriteFile is called. C

#include <C_CkPdf.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPdf pdf;
    HCkJsonObject json;
    HCkJsonObject jsonOut;
    HCkPdf checker;
    HCkJsonObject info;
    HCkPdf reader;

    success = FALSE;

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  The PDF used in this example is available at two_page_memo.pdf

    pdf = CkPdf_Create();
    success = CkPdf_LoadFile(pdf,"qa_data/pdf/two_page_memo.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        return;
    }

    //  The passwords are taken from these two properties at the time Protection is called.
    //  The user password opens the PDF.  The owner password opens it too, and is the one needed
    //  later to change or remove the protection.
    CkPdf_putUserPassword(pdf,"user-secret");
    CkPdf_putOwnerPassword(pdf,"owner-secret");

    //  An empty JSON asks for the defaults: AES-256, everything encrypted, every permission granted.
    json = CkJsonObject_Create();
    jsonOut = CkJsonObject_Create();
    success = CkPdf_Protection(pdf,"encrypt",json,jsonOut);
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkJsonObject_Dispose(jsonOut);
        return;
    }

    //  Nothing has been encrypted yet.  "pending" describes the security the PDF will be saved with.
    printf("algorithm: %s\n",CkJsonObject_stringOf(jsonOut,"pending.algorithm"));
    printf("PDF version: %s\n",CkJsonObject_stringOf(jsonOut,"pending.pdfVersion"));
    printf("password needed to open: %d\n",CkJsonObject_BoolOf(jsonOut,"pending.userPasswordRequired"));

    //  Writing the file applies it.
    success = CkPdf_WriteFile(pdf,"qa_output/memo_encrypted.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(pdf));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkJsonObject_Dispose(jsonOut);
        return;
    }

    //  PreLoadCheck reports a file's encryption without loading it, and needs no password.
    checker = CkPdf_Create();
    info = CkJsonObject_Create();
    success = CkPdf_PreLoadCheck(checker,"qa_output/memo_encrypted.pdf",info);
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(checker));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkJsonObject_Dispose(jsonOut);
        CkPdf_Dispose(checker);
        CkJsonObject_Dispose(info);
        return;
    }

    printf("encrypted: %d\n",CkJsonObject_BoolOf(info,"encrypted"));
    printf("openPasswordRequired: %d\n",CkJsonObject_BoolOf(info,"openPasswordRequired"));

    //  With the password, the PDF opens normally.
    reader = CkPdf_Create();
    CkPdf_putUserPassword(reader,"user-secret");
    success = CkPdf_LoadFile(reader,"qa_output/memo_encrypted.pdf");
    if (success == FALSE) {
        printf("%s\n",CkPdf_lastErrorText(reader));
        CkPdf_Dispose(pdf);
        CkJsonObject_Dispose(json);
        CkJsonObject_Dispose(jsonOut);
        CkPdf_Dispose(checker);
        CkJsonObject_Dispose(info);
        CkPdf_Dispose(reader);
        return;
    }

    printf("pages: %d\n",CkPdf_getNumPages(reader));

    //  Sample output:

    //  algorithm: aes-256
    //  PDF version: 1.7
    //  password needed to open: True
    //  encrypted: True
    //  openPasswordRequired: True
    //  pages: 2


    CkPdf_Dispose(pdf);
    CkJsonObject_Dispose(json);
    CkJsonObject_Dispose(jsonOut);
    CkPdf_Dispose(checker);
    CkJsonObject_Dispose(info);
    CkPdf_Dispose(reader);

    }