C++：Why I can’t open this PDF file created by this C++ program ?

This originally is a simple example used in Larry’s book ,now I changed "std::ofstream fileOutput("quotes.txt ", std::ios::app);" to " std::ofstream fileOutput("quotes.pdf ", std::ios::app);" so as to creat a PDF file (I think !!!), When I compile and run using Dev C++ on Windows XP, it certainly created a quotes.pdf file,but I was not able to open it with Adobe reader , every time when I try to open it ,The Adobe reader always shows that “Adobe Reader couldn’t open “quotes.pdf”,because it is either not a supported file type or because the file has been damaged (for example ,it was sent as an email attachment and wasn’t correctly decoded )”,so what’s wrong here ? Can anyone help me with this?

// quote2.cpp - Script 4.8

// We need the iostream file in order
// to use cout and cin.
#include <iostream>

// We need the string file
// for the string functionality.
#include <string>

// We need the fstream file in order
// to work with files.
#include <fstream>

// Start the main function.
int main() {

// Declare the necessary variables.
std::string quote, speaker;

// Prompt the user for the quotation.
std::cout << "Enter a quotation (without quotation marks):\n";
std::getline(std::cin, quote);

// No extraneous input to be discarded
// because all input is assigned to the string!

// Prompt the user for the quotation's author.
std::cout << "Enter the person to whom this quote is attributed:\n";
std::getline(std::cin, speaker);

// Create a blank line in the output.
std::cout << "\n";

// Repeat the input back to the user.
std::cout << "The following quote has been received...\n\n"
<< quote << "\n-" << speaker << "\n\n";

// Write the data to the file.

// Define a file object.
std::ofstream fileOutput("quotes.pdf", std::ios::app);

// If the file is open, record the data.
if (fileOutput.is_open()) {

// Write the data to the file.
fileOutput << quote << "|"
<< speaker << "\n";

// Close the stream.
fileOutput.close();

// Print a message.
std::cout << "The data has been written to the file!\n";

} else { // Couldn't open the file.
std::cout << "The file could not be opened!\n";
return 1; // Indicates a problem occurred.
}

// Wait for the user to press Enter or Return.
std::cout << "Press Enter or Return to continue.\n";
std::cin.get();

// Return the value 0 to indicate no problems.
return 0;

} // End of the main() function.