The button contains vector graphics for the icons and is designed with relative CSS mark-up. This means that it will still look good if you scale it to anything larger.
You can do that by adding an inline style to the anchor.
The button will then render larger.
<a title='Peecho Print Button' href='http://www.peecho.com/' class='peecho-print-button' data-filetype='pdf' data-width='210' data-height='297' data-pages='32' data-src='https://peecho-assets.s3.amazonaws.com/storage/flight-images/pdf/demo/peecho-book-portrait-297x210mm-32pages.pdf' data-thumbnail='https://peecho-assets.s3.amazonaws.com/storage/flight-images/demo/book.jpg' style="font-size:200%">Print</a>