Create code using solidity to download .pdf files and compile the files into a smart contract

pragma solidity >=0.4.22 <0.7.0;

contract PdfDownloader {
    // address of the contract
    address payable _owner = msg.sender;
    
    // pdf file to be downloaded
    string pdf = "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf";
    
    // how much to pay for the file
    uint256 _price = msg.value;
    
    struct User {
        address addr;
        uint256 balance;
    }
    
    mapping(address => User) public users;
    
    // get the pdf file and pay the price
    function getFile() payable public {
        require(msg.value == _price);
        users[msg.sender].balance = msg.value;
    }
    
    // refund the user if they download the file again
    function refund() public {
        require(msg.value == _price);
        users[msg.sender].balance = msg.value;