You can use the system command (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vclib/html/_crt_system.2c_._wsystem.asp).

    int err = system("pdftk A=test2.pdf cat A4 A7 output test.pdf");

The combination of err (local variable receiving return value of system call) and errno (global variable defined in stdlib.h) tell you the outcome of the command.

There are several methods for launching another program from one program.
You can use _spawn(), _exec(), system(), WinExec(), ShellExecute(), ShellExecuteEx(), and CreateProcess().

The system() function is a more portable function.
WinExec(), ShellExecute(), ShellExecuteEx(), and CreateProcess() are unique to Windows programming.  All four windows functions allow for launching an application in the background (window-hidden).

The WinExec() is the easiest of the four to use.  It only takes two arguments, however MS recommends using the CreateProcess() instead of WinExec on all 32-bit programs.

The ShellExecute() is easier to setup then CreateProcess, and it has more options then WinExec.  However, it's also a legacy function.  MS recommends using ShellExecuteEx() for Win32 applications.
HINSTANCE ShellExecute(
    HWND hwnd,
    LPCTSTR lpVerb,
    LPCTSTR lpFile,
    LPCTSTR lpParameters,
    LPCTSTR lpDirectory,
    INT nShowCmd
);

The ShellExecuteEx() only takes one parameter, but the parameter is a structure with many members, and it's almost as compicate as the CreateProcess() function.
BOOL ShellExecuteEx(
    LPSHELLEXECUTEINFO lpExecInfo
);


The CreateProcess() function takes 10 parameters, and can be tricky to use.
int system( const char *command );
UINT WinExec(
  LPCSTR lpCmdLine,  // address of command line
  UINT uCmdShow      // window style for new application
);
BOOL CreateProcess(
  LPCTSTR lpApplicationName,
                         // pointer to name of executable module
  LPTSTR lpCommandLine,  // pointer to command line string
  LPSECURITY_ATTRIBUTES lpProcessAttributes,  // process security attributes
  LPSECURITY_ATTRIBUTES lpThreadAttributes,   // thread security attributes
  BOOL bInheritHandles,  // handle inheritance flag
  DWORD dwCreationFlags, // creation flags
  LPVOID lpEnvironment,  // pointer to new environment block
  LPCTSTR lpCurrentDirectory,   // pointer to current directory name
  LPSTARTUPINFO lpStartupInfo,  // pointer to STARTUPINFO
  LPPROCESS_INFORMATION lpProcessInformation  // pointer to PROCESS_INFORMATION
);

Or if you need some advanced output processing - check this samples
http://codeproject.com/system/console_spawn_class.asp
http://www.codeproject.com/threads/consolepipe.asp