easy.so you can add this gadget to your blogger.follow below steps.
1. Log in to blogger account and Go to Design > Edit HTML
2. Put checked marked in Expand Widget Templates
3. Find this tag by using Ctrl+F
4. Paste below code before </head> tag
<style type="text/css" media="print">
#noprint {display: none;}
body {background:fff; color:000;}
a {text-decoration: underline; color:00f;}
}
</style>
/*URL: http:www.bloggertrix.com */
5.After paste it find this code <data:post.body/>..
6. If you want to add print this above your post, paste below code before, <data:post.body/>tag
7. If you want to add print this below your post paste below code after <data:post.body/> tag
<a href="javascript:window.print()">Print Page</a>
8 .Click preview and check its safe to save the template.If it ok click save template.
you are done.