Override javascript parameters on a protected page with Greasemonkey?

Question

I'm trying to enable printing on a page which has disabled printing (and downloading). The code below is made with Flip PDF Professional.

At the bottom of the javascript below, I would like to change

bookConfig.enablePrint="No"; and bookConfig.enableDownload="No";

to bookConfig.enablePrint="Yes"; and bookConfig.enableDownload="Yes";

Any idea?

<script language="javascript">  
    var aliasConfig = {
    ... ...
    }
    var bookConfig = {
    ... ...
    }
    bookConfig.bookTitle="www.FlipBuilder.com";

    ...
    bookConfig.enablePrint="Yes";
    bookConfig.enableDownload="Yes";
    bookConfig.enableFlipSound="Enable";
    ...
</script>