How to Encrypt PDF files using Foxit PDF SDK (Objective-C)

Foxit PDF SDK provides a range of encryption and decryption functions to meet different levels of document security protection. Users can use regular password encryption and certificate-driven encryption, or use their own security handler for custom security implementation. It also provides APIs to integrate with the third-party security mechanism (Microsoft RMS). These APIs allow developers to work with the Microsoft RMS SDK to both encrypt (protect) and decrypt (unprotect) PDF documents.

Note: For more detailed information about the RMS encryption and decryption, please refer to the simple demo “security” in the “examples\simple_demo” folder of the download package.

Example:

How to encrypt a PDF file with a Certificate

#include "FSPDFObjC.h"
...
FSPDFDoc *doc = [[FSPDFDoc alloc] initWithPath:input_file];
FSErrorCode code = [doc load:nil];
if (code != FSErrSuccess) {
    return -1;
}
// Do encryption.
NSMutableArray *envelopes = @[].mutableCopy;
NSMutableData *initial_key = [NSMutableData new];
NSString *cert_file_path = [input_path stringByAppendingPathComponent:@"foxit.cer"];
// GetCertificateInfo is implemented in user side to get information from certificate file.
if (!GetCertificateInfo(cert_file_path, envelopes, initial_key, true, 16)) {
    return -1;
}
FSCertificateSecurityHandler *handler = [[FSCertificateSecurityHandler alloc] init];
FSCertificateEncryptData *encrypt_data = [[FSCertificateEncryptData alloc] initWithIs_encrypt_metadata:YES cipher:FSSecurityHandlerCipherAES envelopes:envelopes];
[handler initialize:encrypt_data encrypt_key:initial_key];
[doc setSecurityHandler:handler];
NSString *output_file = [output_directory stringByAppendingPathComponent:@"certificate_encrypt.pdf"];
[doc saveAs:output_file save_flags:FSPDFDocSaveFlagNoOriginal];
...

How to encrypt a PDF file with Foxit DRM

#include "FSPDFObjC.h"
...
FSPDFDoc *doc = [[FSPDFDoc alloc] initWithPath:input_file];
FSErrorCode code = [doc load:nil];
if (code != FSErrSuccess) {
    return -1;
}
// Do encryption.
FSDRMSecurityHandler *handler = [[FSDRMSecurityHandler alloc] init];
NSString *file_id = @"Simple-DRM-file-ID";
NSData *initialize_key = [@"Simple-DRM-initialize-key" dataUsingEncoding:NSUTF8StringEncoding];
FSDRMEncryptData *encrypt_data = [[FSDRMEncryptData alloc] initWithIs_encrypt_metadata:TRUE sub_filter:@"Simple-DRM-filter" cipher:FSSecurityHandlerCipherAES key_length:16 is_owner:YES user_permissions:0xfffffffc];
[handler initialize:encrypt_data file_id:file_id initial_key:initialize_key];
[doc setSecurityHandler:handler];
NSString *output_file = [output_directory stringByAppendingPathComponent:@"foxit_drm_encrypt.pdf"];
[doc saveAs:output_file save_flags:FSPDFDocSaveFlagNoOriginal];
...